fix(rag): KI-111 — wrap collection.query() to survive corrupted Chroma index

User screenshot showed 'Hmm, something went wrong on my end' on every
English chat turn. Local repro of 'Can you help me purchase or find a
health insurance policy?' confirmed rag/retrieve.py:267 raises
ChromaDB InternalError 'Error executing plan: Internal error: Error
finding id' — HNSW index entry pointing to a missing doc, likely from
a partial KI-102 profile-chunk write that corrupted collection state.

KI-107 wrapped only collection.get(); query() had the same failure mode.
Wrap it too — on exception log WARNING + degrade to empty retrieval so
the brain still answers (acknowledging no catalog access) instead of
every turn returning KI-106's generic exception fallback.

Underlying corruption (the index repair / re-ingest) tracked separately.

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

rag/retrieve.py

@@ -263,20 +263,37 @@ async def retrieve(
 
     collection = get_collection()
 
-    # Standard retrieval
-    res = collection.query(
-        query_embeddings=[query_vec],
-        n_results=effective_top_k,
-        where=where,
-    )
-
+    # Standard retrieval — KI-108 (2026-05-15) wraps collection.query() with
+    # the same defensive pattern as KI-107's _safe_collection_get. Live test
+    # post-KI-107 caught the bare query raising
+    # `chromadb.errors.InternalError: Error executing plan: Internal error:
+    # Error finding id` on EVERY user turn (HNSW index entry pointing to a
+    # missing doc — likely from a partial KI-102 profile-chunk write
+    # corrupting the collection state). KI-107 only wrapped .get(); .query()
+    # has the same failure mode. On error we degrade to empty retrieval:
+    # the brain still answers (acknowledging it can't access the catalog)
+    # instead of the user seeing KI-106's generic "something went wrong"
+    # fallback for every message.
     out: list[RetrievedChunk] = []
-    if res["ids"] and res["ids"][0]:
-        for cid, doc, meta, dist in zip(
-            res["ids"][0], res["documents"][0],
-            res["metadatas"][0], res["distances"][0],
-        ):
-            out.append(_build_chunk(cid, doc, meta, 1.0 - dist))
+    try:
+        res = collection.query(
+            query_embeddings=[query_vec],
+            n_results=effective_top_k,
+            where=where,
+        )
+        if res["ids"] and res["ids"][0]:
+            for cid, doc, meta, dist in zip(
+                res["ids"][0], res["documents"][0],
+                res["metadatas"][0], res["distances"][0],
+            ):
+                out.append(_build_chunk(cid, doc, meta, 1.0 - dist))
+    except Exception as e:
+        import logging
+        logging.warning(
+            "Chroma collection.query() failed (top_k=%d, where=%s); "
+            "degrading to empty retrieval. %s: %s",
+            effective_top_k, where, type(e).__name__, str(e)[:300],
+        )
 
     # Profile boost pass — when the orchestrator passes a session_id, look
     # up THAT user's profile chunk in Chroma. Inject it at the top of the