Start on live transcription and python sidecar (faster-whisper)

tests/server-engine.md

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+# Manual verification: server engine (M5, D-013)
+
+The dev environment has no Python package manager and no browser, so — like
+`tests/offline.md` and `tests/live.md` — the real-inference path needs a
+manual run on a machine with Python ≥ 3.9. Everything protocol- and
+HTTP-level is already covered by `bun test` (`tests/transcribe.test.ts`
+exercises the real `Bun.spawn` supervisor against
+`tests/fixtures/fake_sidecar.py`, plus the degradation paths against the real
+`server-py/sidecar.py`).
+
+## 1. Install the sidecar dependencies
+
+```sh
+python3 -m pip install -r server-py/requirements.txt
+```
+
+## 2. Opt-in automated pass (no browser needed)
+
+```sh
+FW_INTEGRATION=1 bun test tests/transcribe.test.ts
+```
+
+Runs the real sidecar end to end (spawn → ready handshake → `tiny.en` load →
+transcribe → done). First run downloads ~75 MB of weights from the Hub.
+
+- [ ] The `real faster-whisper sidecar` describe block passes.
+
+## 3. In-browser run (both engines, same audio)
+
+1. `bun run dev`, open the app, register/sign in.
+2. `GET /api/transcribe/status` (with the session cookie) returns
+   `{"available": true}` — e.g. check the Network tab.
+3. Pick `Whisper Tiny (English)`; transcribe a short clean English clip
+   (e.g. the JFK "ask not…" sample) **on device**. Note the transcript.
+4. Switch the engine toggle to **Server** (visible only while signed in;
+   requires the M5 UI wiring — until that lands, drive it manually:
+   `curl -X POST --data-binary @audio.f32 -b "sid=…" \
+    "http://localhost:3000/api/transcribe?model=onnx-community/whisper-tiny.en"`
+   where `audio.f32` is raw float32 mono 16 kHz PCM).
+5. Transcribe the same clip through the server engine.
+
+- [ ] Segments stream in as JSON lines (not one blob at the end).
+- [ ] Both transcripts agree in content (minor punctuation/casing drift
+      between Transformers.js and faster-whisper is expected).
+- [ ] Signed out, the toggle is gone and `POST /api/transcribe` answers 401.
+- [ ] Second request on the same model is visibly faster (no reload —
+      warm-up strategy).
+- [ ] `AUTH_ENABLED=false bun run dev`: `/api/transcribe*` answers 404 and
+      the anonymous browser flow is unaffected.
+
+When this passes, check off the M5 integration item in `WorkBreakdown.md`.