feat(rag): honest deflection gate with amber UI state and alternative-question chips

app/rag/retriever.py

@@ -64,6 +64,22 @@ def retrieve(
     ]
 
 
+def weak_hit_titles(chunks: Sequence[RetrievedChunk]) -> list[str]:
+    """Distinct parent-document titles of *chunks*, best chunk score first.
+
+    Deflection mode (PLAN §6, A8) is built from these *titles only* — the
+    LOW prompt and the "Maybe try" chips never see document content.
+    """
+    titles: list[str] = []
+    seen: set[uuid.UUID] = set()
+    for rc in sorted(chunks, key=lambda c: c.score, reverse=True):
+        if rc.document.id in seen:
+            continue
+        seen.add(rc.document.id)
+        titles.append(rc.document.title)
+    return titles
+
+
 def select_documents(
     chunks: Sequence[RetrievedChunk],
     n: int | None = None,