chore: code health review - test fix and error comments (bd-9g1z, bd-ork0)

- Remove TestFindJSONLPathDefault from .test-skip (now passes)
- Add explanatory comments to 24 ignored error locations in cmd/bd:
  - Cobra flag methods (MarkHidden, MarkRequired, MarkDeprecated)
  - Best-effort cleanup/close operations
  - Process signaling operations

Part of code health review epic bd-tggf.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

cmd/bd/snapshot_manager.go

@@ -192,6 +192,7 @@ func (sm *SnapshotManager) Cleanup() error {
 	basePath, leftPath := sm.getSnapshotPaths()
 	baseMetaPath, leftMetaPath := sm.getSnapshotMetadataPaths()
 
+	// Best-effort cleanup of snapshot files (may not exist)
 	_ = os.Remove(basePath)
 	_ = os.Remove(leftPath)
 	_ = os.Remove(baseMetaPath)