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/index.md

@@ -12,7 +12,6 @@ went sideways, open an investigation.
 | 2026-07-06 | [Consolidate Oikos control plane onto mac-mini](2026-07-06-consolidate-oikos-control-plane-onto-mac-mini.md) | In Progress (Phase 1-6 implemented, pending cutover) |
 | 2026-07-07 | [Client lifecycle in Go — enrollment through deprecation](2026-07-07-client-lifecycle-in-go.md) | Planned |
 | 2026-07-07 | [Comprehensive audit: stale files, state gaps, and next steps](2026-07-07-comprehensive-audit-and-next-steps.md) | Planned |
-| 2026-07-07 | [DB as single source of truth for agent knowledge](2026-07-07-db-as-source-of-truth.md) | Proposed |
 | 2026-07-08 | [Plan vs implementation cross-reference](2026-07-08-plan-implementation-audit.md) | Planned |
 
 ## Done
@@ -28,6 +27,7 @@ See [`done/`](done/) for executed plans:
 | 2026-06-24 | [TRMNL plugins LXC (128) + middleware deploy pipeline](done/2026-06-24-trmnl-plugins-lxc.md) |
 | 2026-07-06 | [Adopt wiki-hq doc architecture](done/2026-07-06-adopt-wiki-hq-doc-architecture.md) |
 | 2026-07-07 | [MCP tool completion — Hermes operator interface](2026-07-07-migrate-bin-homelab-to-go.md) |
+| 2026-07-07 | [DB as single source of truth for agent knowledge](2026-07-07-db-as-source-of-truth.md) |
 
 ## Conventions