docs(fb-37): wire schema + README + SMOKE + INDEX + SKILL

docs/SMOKE.md

@@ -206,6 +206,22 @@ kebab search "rust" --doc-id "<doc-id>" --tag rust --json
 Bad `--ingested-after` → `error.v1.code = config_invalid`, exit 2.
 Unknown `--media` value → silently empty (no error).
 
+### Trace + stats (fb-37)
+
+Re-run a search with `--trace` to see per-stage candidate lists + timing:
+
+```bash
+kebab --config /tmp/kebab-smoke/config.toml search "rust async" --trace --json | jq .trace
+```
+
+Inspect the corpus health surface:
+
+```bash
+kebab --config /tmp/kebab-smoke/config.toml schema --json | jq .stats
+```
+
+Look for: `media_breakdown` (5 keys), `lang_breakdown`, `index_bytes`, `stale_doc_count`.
+
 ## P6-4 이미지 ingestion 옵션
 
 `config.toml` 에 다음 절을 추가하면 `kebab ingest` 가 `**/*.png` / `**/*.jpg` 등 이미지 자산도 함께 색인합니다 (텍스트만 색인하려면 생략):

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

@@ -54,6 +54,30 @@
             { "type": "string", "format": "date-time" },
             { "type": "null" }
           ]
+        },
+        "media_breakdown": {
+          "type": "object",
+          "description": "p9-fb-37: per-media-kind doc count. 5 keys (markdown/pdf/image/audio/other), zero-padded.",
+          "additionalProperties": { "type": "integer", "minimum": 0 }
+        },
+        "lang_breakdown": {
+          "type": "object",
+          "description": "p9-fb-37: per-language doc count. NULL lang keyed as the literal string 'null'. Map may be empty on empty corpus.",
+          "additionalProperties": { "type": "integer", "minimum": 0 }
+        },
+        "index_bytes": {
+          "type": "object",
+          "description": "p9-fb-37: on-disk byte sums.",
+          "required": ["sqlite", "lancedb"],
+          "properties": {
+            "sqlite":  { "type": "integer", "minimum": 0 },
+            "lancedb": { "type": "integer", "minimum": 0 }
+          }
+        },
+        "stale_doc_count": {
+          "type": "integer",
+          "minimum": 0,
+          "description": "p9-fb-37: docs whose updated_at exceeds config.search.stale_threshold_days. 0 when threshold=0."
         }
       }
     }

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

@@ -9,6 +9,26 @@
     "schema_version": { "const": "search_response.v1" },
     "hits":           { "type": "array", "description": "search_hit.v1[]" },
     "next_cursor":    { "type": ["string", "null"], "description": "Opaque base64 cursor for next page; null when no more hits." },
-    "truncated":      { "type": "boolean", "description": "True when budget forced snippet shortening or k reduction. Independent of `next_cursor`: caller may widen `max_tokens` (re-issue same query) or follow `next_cursor` (advance through more hits) or both." }
+    "truncated":      { "type": "boolean", "description": "True when budget forced snippet shortening or k reduction. Independent of `next_cursor`: caller may widen `max_tokens` (re-issue same query) or follow `next_cursor` (advance through more hits) or both." },
+    "trace": {
+      "type": "object",
+      "description": "p9-fb-37: present iff caller passed --trace / SearchOpts.trace=true. Lex/vec pre-fusion lists + RRF union + per-stage timing.",
+      "required": ["lexical", "vector", "rrf_inputs", "timing"],
+      "properties": {
+        "lexical":   { "type": "array", "items": { "type": "object" } },
+        "vector":    { "type": "array", "items": { "type": "object" } },
+        "rrf_inputs":{ "type": "array", "items": { "type": "object" } },
+        "timing": {
+          "type": "object",
+          "required": ["lexical_ms", "vector_ms", "fusion_ms", "total_ms"],
+          "properties": {
+            "lexical_ms": { "type": "integer", "minimum": 0 },
+            "vector_ms":  { "type": "integer", "minimum": 0 },
+            "fusion_ms":  { "type": "integer", "minimum": 0 },
+            "total_ms":   { "type": "integer", "minimum": 0 }
+          }
+        }
+      }
+    }
   }
 }