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>

docs/wire-schema/v1/bulk_search_response.schema.json

@@ -0,0 +1,24 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://kb.local/wire/v1/bulk_search_response.schema.json",
+  "title": "BulkSearchResponse v1",
+  "description": "p9-fb-42: MCP envelope for bulk_search. CLI emits raw `bulk_search_item.v1` ndjson without this envelope (summary on stderr).",
+  "type": "object",
+  "required": ["schema_version", "results", "summary"],
+  "properties": {
+    "schema_version": { "const": "bulk_search_response.v1" },
+    "results": {
+      "type": "array",
+      "items": { "type": "object", "description": "bulk_search_item.v1" }
+    },
+    "summary": {
+      "type": "object",
+      "required": ["total", "succeeded", "failed"],
+      "properties": {
+        "total":     { "type": "integer", "minimum": 0 },
+        "succeeded": { "type": "integer", "minimum": 0 },
+        "failed":    { "type": "integer", "minimum": 0 }
+      }
+    }
+  }
+}