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/restart-context-cli.ts

@@ -5,7 +5,7 @@ function printUsageAndExit(): never {
   console.error(
     [
       'Usage:',
-      '  tsx src/restart-context-cli.ts write --chat-jid <jid> --summary <text> [--verify <text> ...] [--service-id <id> ...]',
+      '  bun src/restart-context-cli.ts write --chat-jid <jid> --summary <text> [--verify <text> ...] [--service-id <id> ...]',
     ].join('\n'),
   );
   process.exit(1);