fix(fb-33): address PR #124 round 1 review

- pipeline: refresh module docstring step 5 to reflect new cancel
  semantics (RetrievalDone/Token/Final + LlmStreamAborted)
- wire schema: spell out refusal-path behavior in answer_event.v1
  description (only retrieval_done emitted; no final)
- test: factual comment on relax_score_gate-using test corrected
- test: new Ollama-gated stream_score_gate_refusal_emits_only_retrieval_done
- test: new ask_emits_no_final_when_cancelled_mid_stream pinning
  the no-Final invariant on cancel
- pipeline: large_enum_variant comment broadened to acknowledge
  RetrievalDone.hits as the dominant per-emit cost
- HOTFIXES: log AskOpts.stream_sink internal API break per spec
  contract policy

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tasks/HOTFIXES.md

@@ -14,6 +14,19 @@ historical contract that was implemented; this file accumulates the
 deltas so phase 5+ readers can find the live behavior without diffing
 git history.
 
+## 2026-05-09 — p9-fb-33: AskOpts.stream_sink type widened to StreamEvent
+
+**무엇이 바뀌었나**: `kebab_rag::AskOpts.stream_sink` 의 타입이 `Option<mpsc::Sender<String>>` 에서 `Option<mpsc::Sender<StreamEvent>>` 로 변경됨. `kebab_app::StreamEvent` 가 새 re-export.
+
+**Spec contract 와의 관계**: spec §Domain API change 에서 명시한 internal API breaking. consumer = TUI worker 한 곳 (이번 PR 에서 같이 갱신). 외부 consumer 없음.
+
+**의식적 결정**:
+- single sink 로 retrieval / token / final 세 stage 를 모두 운반하기 위한 필수 타입 변경.
+- 기존 `Sender<String>` 으로는 retrieval / final 단계를 표현할 방법이 없음.
+- internal API 라 wire schema 와 다름 — `answer_event.v1` 는 신규 schema (additive minor at wire layer).
+
+**영향 받는 consumer**: `kebab-tui::ask::spawn_ask_worker` (PR #124 에서 동시 갱신). 외부 통합 없음.
+
 ## 2026-05-09 — p9-fb-32: search_hit.v1 / citation.v1 required-field expansion
 
 **무엇이 바뀌었나**: `search_hit.v1` 과 `citation.v1` 의 `required` 배열에 `indexed_at` (RFC3339) + `stale` (bool) 두 필드가 추가됨. `schema_version` 은 그대로 (`search_hit.v1` / `citation.v1`).