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

README.md

@@ -247,6 +247,14 @@ embedded.
   stdlib `ast`) and their title comes from the file stem.
 - Unchanged files are **not re-embedded** — only new/changed ones, so
   refreshes are cheap.
+- After a run that **changed** the knowledge base (at least one document
+  added or updated), the import also regenerates the stored **KB
+  overview** — a plain-text outline of the KB's basic categories that
+  every chat turn injects into the system prompt as `<knowledge_base>`
+  (phase 31). The regeneration is best-effort and change-gated: unchanged
+  re-imports and `--limit` debug runs skip it (no `lite` call), and a
+  `lite`-model failure leaves the previous outline intact without failing
+  the import. The summary line ends `overview=updated|skipped|failed`.
 - To sanity-check the LLM backend (models + embedding dimension) after any
   aipi change: `uv run python -m scripts.llm_probe`.
 
@@ -454,6 +462,8 @@ served locally (no CDN), `BOR_ENVIRONMENT=production`.
 | `BOR_SOURCES_DIR` | `~/bor-sources` | where the `BOR_GIT_SOURCES` repos are cloned/pulled (one subdirectory per repo) |
 | `BOR_STEERING_MAX_CHARS` | `8000` | char budget for the `<tuning>` (steering notes) prompt section |
 | `BOR_SUMMARY_MAX_CHARS` | `12000` | cap on document content sent to the `lite` summary model at import (see *Document summaries*) |
+| `BOR_KB_OVERVIEW_MAX_CHARS` | `4000` | char budget for the `<knowledge_base>` (KB overview) prompt section |
+| `BOR_OVERVIEW_INPUT_MAX_CHARS` | `40000` | cap on the document list sent to the `lite` model when generating the KB overview |
 | `BOR_SUGGESTIONS` | built-in list | JSON list of onboarding chips |
 | `BOR_ADMIN_PASSWORD` | *(required)* | the single admin's password (plaintext, `.env`); app refuses to start when empty |
 | `BOR_SESSION_SECRET` | *(required)* | signing key for the `bor_session` cookie; `python -c 'import secrets;print(secrets.token_hex(32))'` |