feat(v2/approvals): bundle install_packages + rebuild into one approval

Install approval now auto-rebuilds the image and kills the container,
replacing the prior two-card flow where the agent had to call
request_rebuild separately after install_packages was approved.

Queues a processAfter=+5s synthetic prompt so the respawned container
verifies the new packages and reports back to the user.

Adds two v2-checklist gaps found along the way:
- /remote-control and /remote-control-end are v1 host-level commands
  not ported to v2
- messaging_groups.admin_user_id is hardcoded null at registration

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

src/delivery.ts

@@ -633,7 +633,7 @@ async function handleSystemAction(
         agentGroup.name,
         'install_packages',
         { apt, npm, reason },
-        `Agent "${agentGroup.name}" requests package installation:\n${packageList}${reason ? `\nReason: ${reason}` : ''}`,
+        `Agent "${agentGroup.name}" requests package install + container rebuild:\n${packageList}${reason ? `\nReason: ${reason}` : ''}`,
       );
       break;
     }