docs(fb-42): wire schema + README + SMOKE + design + SKILL + INDEX

- Add bulk_search_item.v1 + bulk_search_response.v1 wire schemas
- Register both in WIRE_SCHEMAS const
- README: --bulk flag mention + MCP tool list 7→8 (bulk_search)
- SMOKE: bulk multi-query walkthrough (CLI + MCP equivalent)
- Design §2.2: Bulk multi-query (fb-42) subsection (additive minor)
- SKILL: mcp__kebab__bulk_search section + tool table row
- Task spec status open→completed, banner replaced
- INDEX: fb-42 row 머지 (rerank hint deferred)
- Fix: missed Capabilities {bulk_search} in cli wire.rs test (Task 7 leftover)
- Fix: missed tools.len() 7→8 in cli_mcp_smoke (Task 5 leftover)

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

tasks/INDEX.md

@@ -134,7 +134,7 @@ P0~P5 는 직렬. P6~P9 는 P5 이후 병렬 가능.
 
     ### 🎯 0.6.0 또는 P+ — reasoning
     - [p9-fb-41 multi-hop reasoning](p9/p9-fb-41-multi-hop-reasoning.md) — ⏳ 미구현, brainstorm 필요 (XL, eval 인프라 선행)
-    - [p9-fb-42 bulk multi-query + re-rank hint](p9/p9-fb-42-bulk-multi-query-rerank.md) — ⏳ 미구현, brainstorm 필요 (Nice)
+    - [p9-fb-42 bulk multi-query + re-rank hint](p9/p9-fb-42-bulk-multi-query-rerank.md) — ✅ 머지 (2026-05-10) — bulk only, rerank hint deferred
 
 ## Post-merge 핫픽스