📝 Add configured logger file state API docs

docs/api/configured-logger-file-flush-failures.md

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+---
+name: configured-logger-file-flush-failures
+group: api
+category: runtime
+update-time: 20260512
+description: Read the number of flush failures recorded by the configured runtime file sink.
+key-word:
+    - logger
+    - runtime
+    - file
+    - public
+---
+
+## Configured-logger-file-flush-failures
+
+Read the number of flush failures recorded by a `ConfiguredLogger` file sink. This helper is useful for diagnosing durability-path problems on file-backed loggers.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::file_flush_failures(self : ConfiguredLogger) -> Int {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose flush-failure counter should be inspected.
+
+#### output
+
+- `Int` - Number of recorded flush failures.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- File-backed sinks report their recorded flush-failure count.
+- Queued file sinks forward the metric from the wrapped file sink.
+- Non-file sinks return `0`.
+- The counter is cumulative until reset.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Durability-path Diagnostics
+
+When support output should show flush-path instability:
+```moonbit
+let count = logger.file_flush_failures()
+```
+
+In this example, the configured logger exposes whether flush attempts have been failing.
+
+#### When Inspect Effects Of Auto-flush Policy
+
+When runtime durability tuning should be inspected operationally:
+```moonbit
+ignore(logger.file_flush_failures())
+```
+
+In this example, callers can correlate flush failures with runtime file policy choices.
+
+### Error Case
+
+e.g.:
+- If the configured sink is not file-backed, the method returns `0`.
+
+- If callers need current policy and counters together, `file_state()` is the better API.
+
+### Notes
+
+1. Use this helper when flush-path reliability matters.
+
+2. Pair it with `file_auto_flush()` and `file_flush()` when diagnosing durability behavior.

docs/api/configured-logger-file-open-failures.md

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+---
+name: configured-logger-file-open-failures
+group: api
+category: runtime
+update-time: 20260512
+description: Read the number of open failures recorded by the configured runtime file sink.
+key-word:
+    - logger
+    - runtime
+    - file
+    - public
+---
+
+## Configured-logger-file-open-failures
+
+Read the number of open failures recorded by a `ConfiguredLogger` file sink. This helper is useful for diagnosing file-availability or reopen problems.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::file_open_failures(self : ConfiguredLogger) -> Int {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose open-failure counter should be inspected.
+
+#### output
+
+- `Int` - Number of recorded open failures.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- File-backed sinks report their recorded open-failure count.
+- Queued file sinks forward the metric from the wrapped file sink.
+- Non-file sinks return `0`.
+- The counter is cumulative until reset.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need File Availability Diagnostics
+
+When operators should see whether file open or reopen failed:
+```moonbit
+let count = logger.file_open_failures()
+```
+
+In this example, the configured logger exposes the open-failure metric directly.
+
+#### When Validate Recovery Logic
+
+When tests or support code should inspect whether reopen attempts failed:
+```moonbit
+ignore(logger.file_open_failures())
+```
+
+In this example, the counter helps confirm whether file-open problems occurred during runtime.
+
+### Error Case
+
+e.g.:
+- If the configured sink is not file-backed, the method returns `0`.
+
+- If callers need the full file status snapshot rather than one counter, `file_state()` is the better API.
+
+### Notes
+
+1. Use this helper for focused file-open diagnostics.
+
+2. Pair it with `file_reopen(...)` and `file_available()` during recovery analysis.

docs/api/configured-logger-file-reset-failure-counters.md

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+---
+name: configured-logger-file-reset-failure-counters
+group: api
+category: runtime
+update-time: 20260512
+description: Reset the file failure counters recorded by the configured runtime file sink.
+key-word:
+    - logger
+    - runtime
+    - file
+    - public
+---
+
+## Configured-logger-file-reset-failure-counters
+
+Reset the file failure counters recorded by a `ConfiguredLogger`. This helper clears open, write, flush, and rotation failure metrics together.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::file_reset_failure_counters(self : ConfiguredLogger) -> Bool {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose file failure counters should be cleared.
+
+#### output
+
+- `Bool` - Whether the reset was applied.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- File-backed sinks clear all file failure counters together.
+- Queued file sinks forward the reset behavior to the wrapped file sink.
+- Non-file sinks return `false`.
+- This helper is useful after diagnostics, recovery, or controlled tests.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need A Fresh Diagnostics Baseline
+
+When previous failure history should be cleared before a new observation window:
+```moonbit
+ignore(logger.file_reset_failure_counters())
+```
+
+In this example, future failures can be measured from a clean baseline.
+
+#### When Validate Post-recovery Behavior
+
+When recovery logic should clear old counters before rechecking health:
+```moonbit
+ignore(logger.file_reset_failure_counters())
+ignore(logger.file_open_failures())
+```
+
+In this example, the configured logger starts a new diagnostics window after reset.
+
+### Error Case
+
+e.g.:
+- If the configured sink is not file-backed, the method returns `false`.
+
+- If callers need the current values before clearing them, they should read the counters or `file_state()` first.
+
+### Notes
+
+1. Use this helper after diagnostics or recovery, not before capturing needed evidence.
+
+2. It is the reset companion for the file failure-counter helpers.

docs/api/configured-logger-file-rotation-failures.md

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+---
+name: configured-logger-file-rotation-failures
+group: api
+category: runtime
+update-time: 20260512
+description: Read the number of rotation failures recorded by the configured runtime file sink.
+key-word:
+    - logger
+    - runtime
+    - file
+    - public
+---
+
+## Configured-logger-file-rotation-failures
+
+Read the number of rotation failures recorded by a `ConfiguredLogger` file sink. This helper is useful when runtime rotation behavior should be observed operationally.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::file_rotation_failures(self : ConfiguredLogger) -> Int {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose rotation-failure counter should be inspected.
+
+#### output
+
+- `Int` - Number of recorded rotation failures.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- File-backed sinks report their recorded rotation-failure count.
+- Queued file sinks forward the metric from the wrapped file sink.
+- Non-file sinks return `0`.
+- The counter is cumulative until reset.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Rotation-specific Diagnostics
+
+When support output should reveal whether rotation is failing:
+```moonbit
+let count = logger.file_rotation_failures()
+```
+
+In this example, the configured logger exposes a focused metric for rotation-path health.
+
+#### When Validate Runtime Rotation Tuning
+
+When changed rotation settings should be checked in operation:
+```moonbit
+ignore(logger.file_rotation_failures())
+```
+
+In this example, callers can observe whether runtime rotation changes introduced problems.
+
+### Error Case
+
+e.g.:
+- If the configured sink is not file-backed, the method returns `0`.
+
+- If callers need both rotation config and failure metrics, they should combine this helper with `file_rotation_config()` or `file_state()`.
+
+### Notes
+
+1. Use this helper when diagnosing file rotation reliability.
+
+2. It is especially relevant when runtime rotation policy can change after startup.

docs/api/configured-logger-file-state.md

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+---
+name: configured-logger-file-state
+group: api
+category: runtime
+update-time: 20260512
+description: Read the current file sink snapshot from a configured runtime logger.
+key-word:
+    - logger
+    - runtime
+    - file
+    - public
+---
+
+## Configured-logger-file-state
+
+Read the current file sink snapshot from a `ConfiguredLogger`. This helper exposes path, availability, policy flags, rotation config, and failure counters as one object.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::file_state(self : ConfiguredLogger) -> FileSinkState {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose file state snapshot should be inspected.
+
+#### output
+
+- `FileSinkState` - Current file sink snapshot.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- File-backed sinks return a live snapshot of file state.
+- Queued file sinks forward the snapshot from the wrapped file sink.
+- Non-file sinks return a fallback empty-state snapshot.
+- This helper is broader than individual file counters or policy accessors because it aggregates core file status into one read.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need A Full File Health Snapshot
+
+When diagnostics should inspect runtime file state as one object:
+```moonbit
+let state = logger.file_state()
+```
+
+In this example, callers receive a single file-state snapshot instead of querying each property separately.
+
+#### When Need To Export File Runtime Diagnostics
+
+When a support path should serialize current file state:
+```moonbit
+println(stringify_file_sink_state(logger.file_state(), pretty=true))
+```
+
+In this example, the configured logger snapshot can be exported directly through existing JSON helpers.
+
+### Error Case
+
+e.g.:
+- If the configured sink is not file-backed, the returned snapshot is a fallback empty-style state rather than a live file view.
+
+- If callers also need queue context for queued file sinks, `file_runtime_state()` is the richer API.
+
+### Notes
+
+1. Use this helper for the main one-shot file status snapshot.
+
+2. Prefer it over individual counters when broader file diagnostics are needed.

docs/api/configured-logger-file-write-failures.md

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+---
+name: configured-logger-file-write-failures
+group: api
+category: runtime
+update-time: 20260512
+description: Read the number of write failures recorded by the configured runtime file sink.
+key-word:
+    - logger
+    - runtime
+    - file
+    - public
+---
+
+## Configured-logger-file-write-failures
+
+Read the number of write failures recorded by a `ConfiguredLogger` file sink. This helper is useful for diagnosing runtime write-path problems.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::file_write_failures(self : ConfiguredLogger) -> Int {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose write-failure counter should be inspected.
+
+#### output
+
+- `Int` - Number of recorded write failures.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- File-backed sinks report their recorded write-failure count.
+- Queued file sinks forward the metric from the wrapped file sink.
+- Non-file sinks return `0`.
+- The counter is cumulative until reset.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Runtime Write-path Diagnostics
+
+When support output should show whether writes have been failing:
+```moonbit
+let count = logger.file_write_failures()
+```
+
+In this example, callers get a focused signal for file write-path health.
+
+#### When Compare Sink Health After Recovery
+
+When recovery logic should verify whether new failures still occur:
+```moonbit
+ignore(logger.file_write_failures())
+```
+
+In this example, the metric helps measure whether runtime writes improved after intervention.
+
+### Error Case
+
+e.g.:
+- If the configured sink is not file-backed, the method returns `0`.
+
+- If callers need a fuller view of file health, `file_state()` or `file_runtime_state()` may be better APIs.
+
+### Notes
+
+1. Use this helper for focused write-failure visibility.
+
+2. Pair it with `file_flush_failures()` when diagnosing output-path instability.