chore: update .gitignore to exclude test outputs and debug scripts

Add patterns to ignore temporary files generated during development:
- Test coverage reports (coverage/)
- Downloaded test files (downloads/, *.xlsx, *.parsed.json)
- Debug and manual test scripts (tests/debug/, tests/manual/)
- Temporary test scripts (test-*.mjs, test-*.js, compare_*.js)

This keeps the repository clean while preserving useful test scripts
locally for debugging purposes.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitignore

@@ -5,7 +5,21 @@ out
 .eslintcache
 *.log*
 
-#AI Agent
+# AI Agent
 .claude
 
+# Environment
 .env
+
+# Test outputs
+coverage/
+downloads/
+*.xlsx
+*.parsed.json
+
+# Test scripts (debug and manual)
+tests/debug/
+tests/manual/
+test-*.mjs
+test-*.js
+compare_*.js