Method handleDirEvent

src/sync/watcher.ts:543–561

* Linux per-directory event handler. `filename` is relative to `dir`. A new * sub-directory is picked up by extending the watch tree; everything else is * routed through the shared change handler.

(dir: string, filename: string | Buffer | null)

   * routed through the shared change handler.
   */
  private handleDirEvent(dir: string, filename: string | Buffer | null): void {
    if (this.stopped || filename == null) return;
    const full = path.join(dir, String(filename));

    // A newly-created directory needs its own watch (recursive isn't available
    // on Linux). statSync is cheap and these events are rare relative to file
    // edits. If the path vanished (rapid create/delete) the stat throws and we
    // fall through to the change handler, which no-ops on a non-source path.
    try {
      if (fs.statSync(full).isDirectory()) {
        if (!this.shouldIgnoreDir(full)) this.watchTree(full, /* markExisting */ true);
        return;
      }
    } catch {
      // deleted/inaccessible — treat as a normal change below
    }

    this.handleChange(normalizePath(path.relative(this.projectRoot, full)));
  }

  /**
   * Shared change handler for both watch strategies. `rel` is a