fix(broker): ignore pid/log unlink failures during teardown

[Hughhhhcoder]

Summary

• guard broker teardown's pid/log unlinkSync calls so Windows EPERM/locked-file failures do not abort cleanup
• preserve the existing best-effort teardown behavior for already-removed files
• add a regression test that simulates EPERM on pid/log unlink while confirming teardown still completes and removes the broker socket

Testing

• node --test tests/broker-lifecycle.test.mjs
• ./node_modules/.bin/tsc -p tsconfig.app-server.json

Closes #633.

[Hughhhhcoder]

Status update: the current head remains 2d2d62b1a54c95bc610085f95556052610589fba; local npm test passed (91 tests) and tsc -p tsconfig.app-server.json --noEmit passed. GitHub Pull Request CI is currently action_required with zero jobs, so maintainer approval is needed before CI can run. The full build remains locally blocked only by the prebuild dependency on a global codex app-server generate-ts binary.