chore: replace all node/npm/tsx references with bun across codebase

- Source: setup/service.ts, runners.ts, agent-runner.ts error messages
- Scripts: restart-stack.sh, run-migrations.ts → bun
- Bootstrap: setup.sh check_node→check_bun, npm install→bun install
- Docs: CLAUDE.md, README.md, all SKILL.md files
- Tests: service.test.ts, restart-stack.test.ts expectations updated

src/db.ts

@@ -2271,9 +2271,7 @@ export function claimServiceHandoff(id: number): boolean {
        WHERE id = ?
          AND status = 'pending'`,
   ).run(id);
-  return (
-    (db.prepare('SELECT changes() as c').get() as { c: number }).c > 0
-  );
+  return (db.prepare('SELECT changes() as c').get() as { c: number }).c > 0;
 }
 
 export function completeServiceHandoff(id: number): void {