Method createTempDirForStream

src/node/services/streamManager.ts:833–857

* Create a temporary directory for a stream token * Use ~/.mux-tmp instead of system temp directory (e.g., /var/folders/...) * because macOS user-scoped temp paths are extremely long, which leads to: * - Agent mistakes when copying/manipulating paths * - Harder to read in tool outputs

(streamToken: StreamToken, runtime: Runtime)

   * Uses the Runtime abstraction so temp directories work for both local and SSH runtimes.
   */
  public async createTempDirForStream(streamToken: StreamToken, runtime: Runtime): Promise<string> {
    const tempDir = `~/.mux-tmp/${streamToken}`;

    // Resolve ~ in the runtime's context.
    //
    // IMPORTANT: On Windows local runtime, Git Bash may use a customized $HOME,
    // while runtime.resolvePath expands ~ via Node (USERPROFILE). To avoid drift,
    // create the directory using the resolved absolute path.
    let resolvedPath = (await runtime.resolvePath(tempDir)).trim();

    // In the main process, PlatformPaths defaults to POSIX behavior (no navigator),
    // so we normalize Windows paths to forward slashes.
    if (process.platform === "win32") {
      resolvedPath = resolvedPath.replace(/\\/g, "/");
    }

    try {
      await runtime.ensureDir(resolvedPath);
    } catch (err) {
      const msg = getErrorMessage(err);
      throw new Error(`Failed to create temp directory ${resolvedPath}: ${msg}`);
    }

    return resolvedPath;
  }

  private cleanupStreamTempDir(runtime: Runtime, runtimeTempDir: string): void {
    // Use parent directory as cwd for safety - if runtimeTempDir is malformed,