📝 Add sync config export API docs

docs/api/stringify-text-formatter-config.md

@@ -0,0 +1,104 @@
+---
+name: stringify-text-formatter-config
+group: api
+category: config
+update-time: 20260512
+description: Serialize TextFormatterConfig into compact or pretty JSON text for export and diagnostics.
+key-word:
+    - formatter
+    - config
+    - stringify
+    - public
+---
+
+## Stringify-text-formatter-config
+
+Serialize `TextFormatterConfig` into JSON text. This helper is the highest-level export path when formatter config should be printed, logged, or copied as config text.
+
+### Interface
+
+```moonbit
+pub fn stringify_text_formatter_config(
+  config : TextFormatterConfig,
+  pretty~ : Bool = false,
+) -> String {}
+```
+
+#### input
+
+- `config : TextFormatterConfig` - Formatter config to serialize.
+- `pretty : Bool` - Whether JSON should be pretty-printed.
+
+#### output
+
+- `String` - Serialized JSON text for the formatter config.
+
+---
+
+e.g.:
+```moonbit
+pub fn stringify_text_formatter_config(config : TextFormatterConfig, pretty~ : Bool = false) -> String {}
+```
+
+#### input
+
+- `config : TextFormatterConfig` - Config to stringify.
+- `pretty : Bool` - Pretty-print flag.
+
+#### output
+
+- `String` - JSON text.
+
+---
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- `pretty=false` returns compact JSON.
+- `pretty=true` returns indented JSON for humans.
+- This helper is built on top of `text_formatter_config_to_json(...)`.
+- The output preserves the supported formatter config schema instead of any runtime-only formatter instance details.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Human-readable Formatter Config
+
+When formatter settings should be inspected during setup:
+```moonbit
+println(stringify_text_formatter_config(default_text_formatter_config(), pretty=true))
+```
+
+In this example, the pretty output is suitable for diagnostics or docs.
+
+#### When Need Compact Export Text
+
+When generated config should stay small:
+```moonbit
+let text = stringify_text_formatter_config(
+  TextFormatterConfig::new(show_fields=false),
+)
+```
+
+In this example, compact JSON is returned for storage or transport.
+
+### Error Case
+
+e.g.:
+- If callers need a JSON value for composition, they should use `text_formatter_config_to_json(...)` instead.
+
+- If `style_tags` is empty, the serialized text omits that field rather than forcing an empty object.
+
+### Notes
+
+Notes are here.
+
+1. This helper is useful for config snapshots, examples, and tests.
+
+2. Use `pretty=true` when readability matters.
+
+3. Compact mode is a better default for machine-oriented output.
+
+4. This API exports config data, not formatted records.