memory: a fact written under a new spelling of its key merges into the one that survives ...

The extractor invents a key every time it meets the same fact — `language`,
`preferred_language`, `ui_language` — and the upsert keys on the exact string, so
the base grew several spellings of each durable fact. On prod, 24 facts across 11
clusters share a key once noise prefixes are dropped, 10 of them under the exact
same value.

upsert_fact(dedupe=True) now compares the *tokens* of the normalized key — set
equality, not overlap, and never the value: `ui_language` and `language` are one
key while `dark` and `dark_ui` are two. The row already holding the writer's exact
key wins; otherwise the incoming one does. Losers are marked, not deleted: each
keeps its key and its value and gains `merged_into`, so the merge is reversible
with one UPDATE. Off by default, so the memory tool still writes exactly the row
it asked for.

Every read path filters `merged_into IS NULL`, and the mark is reachable only
where it is meant to be — get_all_facts/fact_count gained include_merged, and
GET /admin/memory?include_merged=true exposes it. search_facts deliberately has
no such flag: the injection path must not be able to see a hidden row. Forgetting
a key drops its hidden aliases first, so none is left pointing at nothing.

Three fixes that fell out of the same read:

- expires_at was overwritten with EXCLUDED.expires_at on every upsert, and the
  extractor always passes None — so it silently cleared any expiry the agent had
  set. Both DO UPDATE clauses now COALESCE.
- The ILIKE fallback was the one read path that served expired facts.
- The `list` action promised "all stored facts" and returned categories. The code
  was right and the description was wrong; the description now says so.

The extraction prompt stopped allowing infrastructure — servers, hosts, addresses,
running services — while the agent and the planner already forbade it; that
loophole is where 423 technical facts came from. It also forbids secrets outright,
and asks for stable snake_case keys. Expiry is now documented as being for facts
with a known end, not for facts you merely doubt.

Facts reach the prompt with their age ("updated 34d ago") alongside confidence:
nothing expires on a clock, so the injection says how old a fact is and lets the
agent weigh it.

Fix memory_summary ON CONFLICT and WebSocket 403 from auth deps ...

- memory/_ddl.py: add UNIQUE(id, user_id) constraint migration for
  memory_summary so ON CONFLICT in set_summary works on existing tables
- auth/deps.py: wrap _resolve_user body in broad try/except so any
  auth resolution failure returns None instead of raising, preventing
  FastAPI dependency system from returning HTTP 403 on WebSocket upgrades

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Fix DDL race condition and PostgreSQL syntax error on startup ...

- _ensure_auth_tables now uses raw asyncpg.connect instead of get_session_store,
  avoiding PgSessionStore._MIGRATE running before navi_users exists
- Move _ensure_auth_tables before ensure_tables in startup so navi_users is
  created before any foreign-key references
- Replace invalid "ADD CONSTRAINT IF NOT EXISTS" with DO $$ block for
  memory_facts_user_cat_key

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Multi-user auth via gnexus-auth OAuth + hybrid role/permission model ...

- Integrate gnexus-auth-client-py (GAuthClient) for OAuth flow, token refresh,
  and webhook parsing
- Add navi/auth/ package: User model, Fernet encryptor, client singleton,
  deps (get_current_user, require_admin, require_permission)
- New tables: navi_users, user_auth_sessions (auto-created on startup)
- Session/memory isolation by user_id with legacy NULL support
- Cookie-based auth proxy: /auth/login, /callback, /logout, /me
- Webhook receiver /webhooks/gnexus-auth handling user events, global logout,
  session revocation, role/permission changes
- Admin endpoints (/admin/*) gated by role + permissions
- Webclient auth store with isAdmin/hasPermission guards
- Admin-only profile filtering in /agents/profiles
- 200/200 tests passing

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Split memory/store.py into focused mixins ...

- _ddl.py: table creation (conditional on pgvector/pg_trgm)
- _embeddings.py: EmbeddingMixin — pgvector checks, embed generation, backfill
- _facts.py: FactMixin — upsert, search (vector + ILIKE), delete, list, count
- _summary.py: SummaryMixin — get/set conversation summary
- _session_state.py: SessionStateMixin — extraction tracking per session
- store.py: reduced to ~60-line facade composing all mixins

No external API changes — MemoryStore remains the single interface.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>