feat: race-free on-wake messages and explicit restart CLI

Decouple container restart from config updates — config CLI ops now only
write to the DB; restart is a separate `ncl groups restart` command with
--rebuild and --message flags. Add on_wake column to messages_in so wake
messages are only picked up by a fresh container's first poll, preventing
dying containers from stealing them during the SIGTERM grace window.
killContainer accepts an onExit callback for race-free respawn. Agent-
called restart auto-scopes to the calling session.

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

src/session-manager.ts

@@ -216,6 +216,11 @@ export function writeSessionMessage(
      * path so the target's reply routes back to that exact session.
      */
     sourceSessionId?: string | null;
+    /**
+     * 1 = only deliver on the container's first poll (fresh start).
+     * Dying containers (past first poll) skip these rows.
+     */
+    onWake?: 0 | 1;
   },
 ): void {
   // Extract base64 attachment data, save to inbox, replace with file paths
@@ -235,6 +240,7 @@ export function writeSessionMessage(
       recurrence: message.recurrence ?? null,
       trigger: message.trigger ?? 1,
       sourceSessionId: message.sourceSessionId ?? null,
+      onWake: message.onWake ?? 0,
     });
   } finally {
     db.close();