Record D-WS2a: hint measurements, the 120-token truncation rule, no faster-whisper hotwords

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/plans/001-2-vocabulary-hint.md

@@ -46,7 +46,7 @@ sidecar applies the same truncation rule (Python twin, parity-tested) and passes
   above it — URL-safe since it travels as a query param).
 - `normalizeHint`: drop control chars, one term per line or comma-separated → lines trimmed, empty
   lines dropped, joined with `", "`, whitespace collapsed. Empty → `""` (= no prompt).
-- `PROMPT_TOKEN_BUDGET = 223` (= 448/2 − 1, the openai/faster-whisper prompt cap).
+- `PROMPT_TOKEN_BUDGET = 120` (measured; was 223 = 448/2 − 1, see D-WS2a).
 - **Truncation rule:** encode `" " + hint`; if > budget, keep the longest prefix of whole
   (space-separated) words that fits, trailing `,;` stripped from the kept text; if not even the
   first word fits, its first 223 tokens. The start of the list is kept, the end dropped.
@@ -179,12 +179,12 @@ Scratch scripts in `/tmp/ws2/` (not committed), importing the worktree's modules
   `"Maxwell, Voices of the Void"`: WER (test normalizer), count of `maxwell` and `voices of the
   void` vs reference counts, wall-clock, punctuation count (a prompt without a final full stop may
   suppress punctuation — if so, `normalizeHint` appends `.` and Task 1 tests are updated).
-- [ ] Short-window hallucination: 1–3 s low-noise and 2 s speech snippets with/without hint, turbo
+- [x] Short-window hallucination: 1–3 s low-noise and 2 s speech snippets with/without hint, turbo
   + small model; output must not contain hint words that are absent from the audio.
-- [ ] Server path (venv, `mobiuslabsgmbh/faster-whisper-large-v3-turbo` cached, int8 CPU):
+- [x] Server path (venv, `mobiuslabsgmbh/faster-whisper-large-v3-turbo` cached, int8 CPU):
   en_alien none / initial_prompt / hotwords / both. Keep hotwords only if it measurably beats
   initial_prompt alone on hinted-word recall without WER loss. Implement the outcome in sidecar.py.
-- [ ] Write D-WS2a (bottom of `docs/Decisions.md`) with numbers labelled CPU/onnxruntime-node,
+- [x] Write D-WS2a (bottom of `docs/Decisions.md`) with numbers labelled CPU/onnxruntime-node,
   truncation rule, wrapper rationale, 4.3.2 check. Architecture.md data-flow note; WorkBreakdown
   tick/noticed. Commit.