feat(FN-1225): add headless fn serve command with health checks

- Add a new serve command implementation that runs the dashboard server in headless mode and exposes a health endpoint
- Register the serve command in CLI routing and extend bin command coverage for dispatch behavior
- Add comprehensive serve command tests for startup flow, options handling, and health-check responses
- Fix mission event ordering in MissionStore to keep health snapshots deterministic under concurrent updates
- Include a changeset for @gsxdsm/fusion documenting the new fn serve capability

packages/core/src/mission-store.ts

@@ -405,7 +405,7 @@ export class MissionStore extends EventEmitter<MissionStoreEvents> {
       SELECT *
       FROM mission_events
       WHERE ${whereSql}
-      ORDER BY timestamp DESC
+      ORDER BY timestamp DESC, rowid DESC
       LIMIT ? OFFSET ?
     `).all(...params, limit, offset) as any[];