Fix prebuilt deployment: install full archive, clean temp dirs, health binary probe

[Copilot]

The bundle-acestep.ts script only deployed ace-lm and ace-synth, discarding all shared libraries (libggml*.so/.dylib/.dll) and helper binaries required at runtime. Temp job directories were also not fully cleaned up, and /health had no actual binary verification.

Changes

• scripts/bundle-acestep.ts — Copy every file from the extracted archive to acestep-runtime/bin/ instead of cherry-picking two executables. The archives contain 20+ files: ace-server, ace-understand, neural-codec, mp3-codec, quantize, and all GGML shared libraries. chmod 0o755 applied to all non-.a files on non-Windows.

• src/worker.ts — Replace the readdir + per-file unlink loop in finally with rm(jobDir, { recursive: true, force: true }). The old approach left the job directory itself on disk and silently missed any subdirectories (e.g. uploaded audio).

• src/index.ts — /health now spawns ace-synth with no arguments (prints usage, exits non-zero — expected) to confirm the binary is present and executable:

  {
    "status": "ok",
    "binary": "ok",
    "binary_path": "/…/acestep-runtime/bin/ace-synth",
    "binary_hint": "Usage: ace-synth --request <json...> …"
  }

  Returns "binary": "unavailable" with an error hint when the binary is missing or fails to start.

• README.md / docs/API.md — Updated distribution tree and health response docs to reflect the above.

---

⌨️ Start Copilot coding agent tasks without leaving your editor — available in VS Code, Visual Studio, JetBrains IDEs and Eclipse.