- Introduce `skipOnWindows` helper to properly skip tests relying on Unix specific paths.
- Replace fixed sleep with `require.Eventually` in `waitForPeerDisconnect` to address flakiness in CI.
- Split `commitFastPath` logic out of `runFastPathSync` to close race conditions and improve clarity.
- Update tests to leverage new helpers and more precise assertions (e.g., `waitForPeerDisconnect`).
- Add `flakyStore` test helper to exercise fail-closed behavior in flag handling.
- Enhance `RunFastPathFlagRoutine` to disable the flag on store read errors.
Gate the peer-sync fast path on a runtime flag polled from Redis so operators can roll the optimisation out gradually and flip it off without a redeploy.
Without NB_PEER_SYNC_REDIS_ADDRESS the routine stays disabled, every Sync runs the full network map path, and no entries accumulate in the peer serial cache — bit-for-bit identical to the pre-fast-path behaviour. When the env var is set, a background goroutine polls the configured key (default "peerSyncFastPath") every minute; values "1" or "true" enable the fast path, anything else disables it.
- RunFastPathFlagRoutine mirrors shared/logleveloverrider: dedicated Redis connection, background ticker, redis.Nil treated as disabled.
- NewServer takes the flag handle; tryFastPathSync and the recordPeerSyncEntry helpers short-circuit when Enabled() is false.
- invalidatePeerSyncEntry still runs on Login regardless of flag state.
- NewFastPathFlag(bool) exposed for tests and callers that need to force a state without going through Redis.
