complete DB as source of truth — FTS knowledge surface

Plan #5 done. Wiki already archived to archive/knowledge/. seeds/knowledge.yaml
has 24 docs + 6 investigations + 3 runbooks.

- MCP search_knowledge: upgraded from ILIKE to PostgreSQL ts_rank/ts_headline
- MCP get_entity_knowledge: new tool, walks relationship edges to return
  all docs/investigations/runbooks linked to an entity
- HTTP endpoints (SearchKnowledge, GetEntityKnowledge) already used full FTS
- Plan index + audit cross-reference updated

plans/2026-07-07-db-as-source-of-truth.md

@@ -1,6 +1,6 @@
 # 2026-07-07 — DB as single source of truth for agent knowledge
 
-**Status:** Proposed
+**Status:** Done (2026-07-08) — wiki archived, FTS live, MCP + HTTP knowledge surface complete.
 
 ## Goal