docs(v0.20.1): polish PR-review findings (README/HOTFIXES/schema/SKILL)

opus PR-level final review (Approved with notes) 의 4 minor finding
mechanical 정정:

1. README.md — `kebab search` row 의 영어 substring 매칭 표현이
   V007 시절 그대로였음. V009 의 whole-token 회귀 (substring → V002
   동작) 를 정직히 명시 + vector/hybrid mode 권장 안내.
2. tasks/HOTFIXES.md — 2026-05-28 entry 의 file path 정정. lexical.rs
   는 lindera 호출자가 아니라 build_match_string 의 MIN_QUERY_CHARS
   3→2 갱신만; lindera helper 의 실제 owner 는 kebab-chunk/src/lib.rs.
   ingest.rs 는 본 PR scope 외, eager backfill hook 위치는 kebab-app/
   src/app.rs::App::open_with_config.
3. docs/wire-schema/v1/search_response.schema.json — `hint` field
   description 이 V007 trigram 3-char minimum 시절 advisory 시그니처
   그대로. v0.20.1 에서 helper retired + always-omit 사실 명시
   (forward-compat 차원에서 field 만 schema 에 보존).
4. integrations/claude-code/kebab/SKILL.md — `hint` field 설명의
   self-contradiction ("present only with trigram in edge cases" vs
   "Korean 2-char now supported") 해소. retired + reuse 가능 명시.

PR-level reviewer recommendation: "Merge as-is — block 사유 아님 (모든
finding minor)". 본 commit 은 reviewer 의 옵션 1 (별 docs hotfix
commit) 채택.

Spec: docs/superpowers/specs/2026-05-28-v0.20.x-korean-morphological-tokenizer-spec.md
Plan: docs/superpowers/plans/2026-05-28-v0.20.x-korean-morphological-tokenizer-plan.md (PR-level finding follow-up)

integrations/claude-code/kebab/SKILL.md

@@ -60,7 +60,7 @@ Input:
 - Cite back to the user as `doc_path § heading_path[-1]` so they can open the source.
 - When `truncated: true`, the budget loop modified the page (snippet shortening or k reduction). `next_cursor` is **independent** — non-null whenever more hits may be reachable. Caller may widen `max_tokens` (re-issue same query for fuller snippets / more hits per page) or follow `next_cursor` (advance through more hits) or both. Mismatched cursor (corpus_revision changed) returns `error.v1.code = stale_cursor` — re-issue the search to obtain a fresh one.
 - **`trace: true` (p9-fb-37)** — debug aid. Response carries an extra `trace` block: `lexical[]` + `vector[]` (pre-fusion candidates), `rrf_inputs[]` (RRF union before final cut), and `timing` (`lexical_ms`, `vector_ms`, `fusion_ms`, `total_ms`). Trace bypasses the search cache (always cold). Use sparingly — it bloats the wire response and is for diagnosing "why did this hit / not hit", not normal retrieval.
-- **`hint` (v0.17.0, v0.20.1 한국어 2자 지원)** — optional advisory string on `search_response.v1`. Present only when the result is empty AND using the trigram tokenizer in certain edge cases. Korean queries now support 2-character words (`한국`, `서울` both hit). For best results use ≥3-character keywords in general queries. Raw FTS5 mode (`'...'`) opts out — the user opted into FTS5 syntax. Vector / hybrid modes carry the field too but it's rarely triggered (semantic embeddings handle short queries).
+- **`hint` (v0.17.0 — v0.20.1 에서 retired)** — forward-compat 차원에서 schema 에 보존된 optional advisory string. v0.20.1 (V009 morphological tokenizer) 이후 한국어 2자 query (`한국`, `서울`) 도 정상 hit 하므로 `short_query_hint` helper 가 제거됨 — 본 field 는 항상 omit. 향후 다른 advisory 가 필요해지면 동일 shape 으로 reuse.
 - **Column scoping (post-v0.17.1 dogfood)** — default lexical / hybrid matching is scoped to the `text` column only. The `heading_path` column is indexed (path segments like `app`, `src` plus JSON punctuation are 3-gram'd) but excluded from the default MATCH — past JSON noise produced false positives where a query coincidentally shared a 3-gram with a file's heading path. To deliberately search heading paths, escape into raw FTS5 mode with an explicit column filter: `'heading_path : <token>'` (e.g. `kebab search "'heading_path : agent'"`). Same applies to MCP `search` — quote the inner expression. Raw mode bypasses both column scoping and the 3-char `hint` short-circuit.
 
 ### `mcp__kebab__bulk_search`