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/sync.go

@@ -1402,7 +1402,7 @@ func exportToJSONL(ctx context.Context, jsonlPath string) error {
 		exportedIDs = append(exportedIDs, issue.ID)
 	}
 
-	// Close temp file before rename
+	// Close temp file before rename (error checked implicitly by Rename success)
 	_ = tempFile.Close()
 
 	// Atomic replace