Memory Dashboard API: REST endpoints for observability

[kovtcharov]

Summary

Build the FastAPI router for the Memory Dashboard. Exposes MemoryStore data via REST API for the frontend dashboard.

Spec: docs/spec/agent-memory-architecture.md → "Observability & Dashboard" → "UI Backend: Memory Router"

Depends on: #542 (MemoryStore)

File: src/gaia/ui/routers/memory.py

Endpoints

Dashboard

• GET /api/memory/stats — aggregate stats (knowledge counts by category/context, conversation/tool totals, upcoming/overdue)
• GET /api/memory/activity?days=30 — daily activity timeline

Knowledge Browser

• GET /api/memory/knowledge — paginated, filterable (category, context, entity, sensitive, search), sortable
• POST /api/memory/knowledge — create entry (source='user', confidence=0.8)
• PUT /api/memory/knowledge/{id} — edit entry (all fields)
• DELETE /api/memory/knowledge/{id} — delete entry

Entities & Contexts

• GET /api/memory/entities — list unique entities with counts
• GET /api/memory/entities/{entity} — all knowledge for an entity
• GET /api/memory/contexts — list contexts with counts

Tool Performance

• GET /api/memory/tools — per-tool stats (calls, success rate, avg duration, last error)
• GET /api/memory/tools/{name}/history — call history for a tool

Errors & Conversations

• GET /api/memory/errors — recent tool errors
• GET /api/memory/conversations — session list with turn counts
• GET /api/memory/conversations/{session_id} — full conversation
• GET /api/memory/conversations/search — FTS5 search
• GET /api/memory/upcoming?days=7 — time-sensitive items

DB Access

• Read operations use read-only connection (?mode=ro)
• Write operations (POST/PUT/DELETE) use short-lived read-write connections
• WAL mode ensures concurrent reader safety

Acceptance Criteria

• All 15 endpoints implemented
• Pagination works on knowledge and tool history
• Filters work (category, context, entity, sensitive, search)
• Stats aggregation is correct
• Activity timeline groups by day correctly
• Router registered in server.py