Fix auto-lookback trigger and add version tracking (#20)

* Fix auto-lookback trigger and add version tracking

- Trigger on stdin inactivity instead of render time
- Only dump when new output exists since last dump
- Default timeout 5s -> 15s
- Embed git hash in version output
- Document macOS config path

CONTRIBUTING.md

@@ -2,6 +2,17 @@
 
 Contributions welcome! Feel free to open issues or pull requests.
 
+## Bug Reports
+
+When filing a bug report, please include the output of `claude-chill --version`:
+
+```
+$ claude-chill --version
+claude-chill 0.1.0 (35ecc80)
+```
+
+This includes the version number and git commit hash, which helps identify exactly which code you're running.
+
 ## Branch naming
 
 - `feature/description`