feat(rag): lite-generated KB overview in the system prompt — stored single row, regenerated on import, <knowledge_base> section in HIGH+LOW prompts

app/config.py

@@ -76,6 +76,17 @@ class Settings(BaseSettings):
     #: and the shared ``[…truncated…]`` marker is appended (see
     #: ``app.rag.summarizer``).
     summary_max_chars: int = 12_000
+    #: Char budget for the ``<knowledge_base>`` section of the system prompt
+    #: (phase 31: lite-generated KB overview, ``app.rag.overview``). The
+    #: newest-fitting prefix of the stored outline is kept and the overflow
+    #: is replaced by the shared ``[…truncated…]`` marker (phase 15
+    #: convention — ``app.rag.prompts``).
+    kb_overview_max_chars: int = 4_000
+    #: Cap on the document list (source/path/title/first summary line per
+    #: row) sent to the ``lite`` overview model in one call (phase 31,
+    #: ``app.rag.overview``). Overflow is cut at the cap and the shared
+    #: ``[…truncated…]`` marker is appended (summarizer convention).
+    overview_input_max_chars: int = 40_000
 
     # --- Hybrid retrieval (A7, revised 2026-08-21) ---
     # cosine top-N ∪ Postgres FTS top-N, fused with Reciprocal Rank Fusion