🙈 chore: exclude planning-with-files from git tracking

- Add planning files (task_plan.md, findings.md, progress.md) to .gitignore
- Remove existing planning files from git index (keep local)
- Update planning-with-files rule with git management policy

These temporary session files should not be version controlled.

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

.gitignore

@@ -230,3 +230,11 @@ tests/data/
 
 # Serena MCP tool config
 .serena/
+
+# Planning-with-files temporary files
+task_plan.md
+findings.md
+progress.md
+task_plan_*.md
+findings_*.md
+progress_*.md