0.22.0 — full MCP agent surface: 19 new tools, async run, session reliability

Stage 1 — Foundation:
- Target validation: iptables + systemctl/docker target-type gates
- Async run for long-running commands (sleep/wait/poll loops)
- audit_log.session_id plumbing (SQL, sqlcgen, 18 call sites)

Stage 2 — External agent observe (11 tools):
- get_dashboard_summary, get_ontology, list_checks, list_executions
- get_knowledge_revisions, get_knowledge_duplicates, get_knowledge_orphans
- list_knowledge_tags, list_entity_sessions, find_entities_by
- 3 resource templates: oikos://entity/{slug}, knowledge/{id}, execution/{id}

Stage 3 — Nomos reliability:
- complete_task(success) refused without verification (upgraded from warn)
- sessionHasPlan excludes replaced steps (forces propose_plan after reopen)
- Bash syntax validation in run() (rejects literal \n, flag-space typos)
- Scope gate in SOUL.md (ask before pivoting to unrelated subsystem)

Stage 4 — External agent act (9 mutation tools):
- ack_signal, resolve_signal, mute_signal, cancel_execution
- update_check, delete_knowledge, restore_knowledge
- merge_knowledge, rename_knowledge_tag

internal/db/sqlcgen/models.go

@@ -398,18 +398,19 @@ type SeedVersion struct {
 }
 
 type SessionPlanStep struct {
-	ID          uuid.UUID
-	SessionID   uuid.UUID
-	Seq         int32
-	Title       string
-	Detail      string
-	Status      string
-	ExecutionID *uuid.UUID
-	TargetSlug  *string
-	StartedAt   *time.Time
-	FinishedAt  *time.Time
-	CreatedAt   time.Time
-	Generation  int32
+	ID             uuid.UUID
+	SessionID      uuid.UUID
+	Seq            int32
+	Title          string
+	Detail         string
+	Status         string
+	ExecutionID    *uuid.UUID
+	TargetSlug     *string
+	StartedAt      *time.Time
+	FinishedAt     *time.Time
+	CreatedAt      time.Time
+	Generation     int32
+	ReplacedReason *string
 }
 
 type SessionQuestion struct {