Register daemon shutdown cleanup before readiness

[tomcasaburi]

GitHub issue:

• Title: Register daemon shutdown cleanup before readiness
• Description: The daemon can print readiness output before its async exit hook is registered, leaving a short window where SIGTERM exits without killing the Kubo child process. The existing daemon shutdown test exposes this as a suite-level timing failure in test/cli/daemon.test.ts.

Discovered while verifying #58. Implementation moved shutdown cleanup registration before Kubo/RPC startup and was verified by the focused shutdown test plus the full CLI suite.

[tomcasaburi]

Implementation update:

• Moved daemon shutdown cleanup registration before Kubo/RPC startup, closing the readiness-before-cleanup SIGTERM race.
• Verified the exact shutdown case with npm run test:cli -- test/cli/daemon.test.ts -t "daemon's own cleanup kills kubo after SIGTERM".\n- Verified the full CLI suite with npm run test:cli: 29 files, 215 passed, 1 skipped.