feat: Phase 4 V1 — Robustness Hardening

Adds the observability + safety layer that turns AtoCore from
"works until something silently breaks" into "every mutation is
traceable, drift is detected, failures raise alerts."

1. Audit log (memory_audit table):
   - New table with id, memory_id, action, actor, before/after JSON,
     note, timestamp; 3 indexes for memory_id/timestamp/action
   - _audit_memory() helper called from every mutation:
     create_memory, update_memory, promote_memory,
     reject_candidate_memory, invalidate_memory, supersede_memory,
     reinforce_memory, auto_promote_reinforced, expire_stale_candidates
   - Action verb auto-selected: promoted/rejected/invalidated/
     superseded/updated based on state transition
   - "actor" threaded through: api-http, human-triage, phase10-auto-
     promote, candidate-expiry, reinforcement, etc.
   - Fail-open: audit write failure logs but never breaks the mutation
   - GET /memory/{id}/audit: full history for one memory
   - GET /admin/audit/recent: last 50 mutations across the system

2. Alerts framework (src/atocore/observability/alerts.py):
   - emit_alert(severity, title, message, context) fans out to:
     - structlog logger (always)
     - ~/atocore-logs/alerts.log append (configurable via
       ATOCORE_ALERT_LOG)
     - project_state atocore/alert/last_{severity} (dashboard surface)
     - ATOCORE_ALERT_WEBHOOK POST if set (auto-detects Discord webhook
       format for nice embeds; generic JSON otherwise)
   - Every sink fail-open — one failure doesn't prevent the others
   - Pipeline alert step in nightly cron: harness < 85% → warning;
     candidate queue > 200 → warning

3. Integrity checks (scripts/integrity_check.py):
   - Nightly scan for drift:
     - Memories → missing source_chunk_id references
     - Duplicate active memories (same type+content+project)
     - project_state → missing projects
     - Orphaned source_chunks (no parent document)
   - Results persisted to atocore/status/integrity_check_result
   - Any finding emits a warning alert
   - Added as Step G in deploy/dalidou/batch-extract.sh nightly cron

4. Dashboard surfaces it all:
   - integrity (findings + details)
   - alerts (last info/warning/critical per severity)
   - recent_audit (last 10 mutations with actor + action + preview)

Tests: 308 → 317 (9 new):
  - test_audit_create_logs_entry
  - test_audit_promote_logs_entry
  - test_audit_reject_logs_entry
  - test_audit_update_captures_before_after
  - test_audit_reinforce_logs_entry
  - test_recent_audit_returns_cross_memory_entries
  - test_emit_alert_writes_log_file
  - test_emit_alert_invalid_severity_falls_back_to_info
  - test_emit_alert_fails_open_on_log_write_error

Deferred: formal migration framework with rollback (current additive
pattern is fine for V1); memory detail wiki page with audit view
(quick follow-up).

To enable Discord alerts: set ATOCORE_ALERT_WEBHOOK to a Discord
webhook URL in Dalidou's environment. Default = log-only.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_memory.py

@@ -264,6 +264,82 @@ def test_expire_stale_candidates(isolated_db):
     assert mem["status"] == "invalid"
 
 
+# --- Phase 4: memory_audit log ---
+
+
+def test_audit_create_logs_entry(isolated_db):
+    from atocore.memory.service import create_memory, get_memory_audit
+
+    mem = create_memory("knowledge", "test content for audit", actor="test-harness")
+    audit = get_memory_audit(mem.id)
+    assert len(audit) >= 1
+    latest = audit[0]
+    assert latest["action"] == "created"
+    assert latest["actor"] == "test-harness"
+    assert latest["after"]["content"] == "test content for audit"
+
+
+def test_audit_promote_logs_entry(isolated_db):
+    from atocore.memory.service import create_memory, get_memory_audit, promote_memory
+
+    mem = create_memory("knowledge", "candidate for promote", status="candidate")
+    promote_memory(mem.id, actor="test-triage")
+    audit = get_memory_audit(mem.id)
+    actions = [a["action"] for a in audit]
+    assert "promoted" in actions
+    promote_entry = next(a for a in audit if a["action"] == "promoted")
+    assert promote_entry["actor"] == "test-triage"
+    assert promote_entry["before"]["status"] == "candidate"
+    assert promote_entry["after"]["status"] == "active"
+
+
+def test_audit_reject_logs_entry(isolated_db):
+    from atocore.memory.service import create_memory, get_memory_audit, reject_candidate_memory
+
+    mem = create_memory("knowledge", "candidate for reject", status="candidate")
+    reject_candidate_memory(mem.id, actor="test-triage", note="stale")
+    audit = get_memory_audit(mem.id)
+    actions = [a["action"] for a in audit]
+    assert "rejected" in actions
+    reject_entry = next(a for a in audit if a["action"] == "rejected")
+    assert reject_entry["note"] == "stale"
+
+
+def test_audit_update_captures_before_after(isolated_db):
+    from atocore.memory.service import create_memory, get_memory_audit, update_memory
+
+    mem = create_memory("knowledge", "original content", confidence=0.5)
+    update_memory(mem.id, content="updated content", confidence=0.9, actor="human-edit")
+    audit = get_memory_audit(mem.id)
+    update_entries = [a for a in audit if a["action"] == "updated"]
+    assert len(update_entries) >= 1
+    u = update_entries[0]
+    assert u["before"]["content"] == "original content"
+    assert u["after"]["content"] == "updated content"
+    assert u["before"]["confidence"] == 0.5
+    assert u["after"]["confidence"] == 0.9
+
+
+def test_audit_reinforce_logs_entry(isolated_db):
+    from atocore.memory.service import create_memory, get_memory_audit, reinforce_memory
+
+    mem = create_memory("knowledge", "reinforced mem", confidence=0.5)
+    reinforce_memory(mem.id, confidence_delta=0.02)
+    audit = get_memory_audit(mem.id)
+    actions = [a["action"] for a in audit]
+    assert "reinforced" in actions
+
+
+def test_recent_audit_returns_cross_memory_entries(isolated_db):
+    from atocore.memory.service import create_memory, get_recent_audit
+
+    m1 = create_memory("knowledge", "mem one content", actor="harness")
+    m2 = create_memory("knowledge", "mem two content", actor="harness")
+    recent = get_recent_audit(limit=10)
+    ids = {e["memory_id"] for e in recent}
+    assert m1.id in ids and m2.id in ids
+
+
 # --- Phase 3: domain_tags + valid_until ---