fix: Windows support - skip directory fsync, green test suite

[KernelPryanic]

Every accepted message crashed on Windows (EPERM: directory fsync), so the spool/outbox never persisted.

• Skip directory fsync on win32 (queue, outbox); file fsync + rename remain
• Fix worker spawn paths (fileURLToPath), POSIX-only test expectations (mode bits, UDS binds, config separators); skip UDS/real-host tests on win32

npm test: 173 pass, 0 fail, 6 skipped on Windows; typecheck clean.