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/migrate.go

@@ -721,9 +721,9 @@ func cleanupWALFiles(dbPath string) {
 	walPath := dbPath + "-wal"
 	shmPath := dbPath + "-shm"
 	
-	// Best effort - don't fail if these don't exist
-	_ = os.Remove(walPath)
-	_ = os.Remove(shmPath)
+	// Best effort cleanup - don't fail if these don't exist
+	_ = os.Remove(walPath) // WAL may not exist
+	_ = os.Remove(shmPath) // SHM may not exist
 }
 
 // handleInspect shows migration plan and database state for AI agent analysis