📝 add example-first documentation paths

docs/extend/index.md

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+# Extend A Logger
+
+Start from an [Example flow](../examples/index.md), then add one extension at a time. These pages explain when an abstraction is useful and which operational boundary it introduces.
+
+## Extension Map
+
+| Need | Extension | Main trade-off |
+| --- | --- | --- |
+| Absorb short output bursts | [Queueing](./queue.md) | You must choose overflow and flush behavior. |
+| Send records to multiple destinations or route by level | [Sink composition](./composition.md) | More explicit construction than presets. |
+| Control terminal appearance | [Text formatting](./formatting.md) | Formatting affects presentation, not record structure. |
+| Share code across native and web targets | [Target boundaries](./targets.md) | File and async runtime behavior differ by backend. |
+
+For exact function signatures, follow each page's links into the [API reference](../api/index.md).