fix(daemon): wait for readiness instead of polling - #31

Summary

• Part 4 of the stack for Idle daemon wakes the CPU ~100 times/s (10 ms sleep in the accept loop) #25, stacked on refactor(daemon): route stop and ownership through Control #30. Please merge fix(daemon): block subscriptions instead of polling #28 → fix(daemon): survive thread spawn failures #29 → refactor(daemon): route stop and ownership through Control #30 first.
• Fixes Idle daemon wakes the CPU ~100 times/s (10 ms sleep in the accept loop) #25 (this PR completes it).
• The Unix daemon loop now sleeps in poll(2) on the listener plus a private wake channel (UnixStream::pair, non-blocking, CLOEXEC) instead of a 10 ms sleep. The timeout is the minimum of the next ownership deadline, a 2 s safety net, and the accept back-off.
• Control notifies under the ownership mutex for every stop/ownership mutation. Control::tick drains the wake channel, observes, detects missed wakes, and ticks under the same lock, so a missed wake is detected deterministically (a warning in release builds; an error in debug builds, with cleanup still running).
• Handler completion wakes the loop, so finished connections close promptly.
• EMFILE-class errors (EMFILE, ENFILE, ENOBUFS, ENOMEM) from accept or cancellation now pause accept for 100 ms instead of killing the daemon.
• Windows keeps its 10 ms poll via stubs. Follow-up: WaitForMultipleObjects on the connect event plus a stop event, and replacing the per-terminal 10 ms root-exit poll.

Measurement (macOS, debug builds, idle owned daemon)

Tests added

• src/daemon/server.rs:
  • owned_handoff_expiry_keeps_daemon
  • idle_loop_does_not_spin
  • connect_does_not_wait_for_timeout
  • handler_completion_closes_socket_promptly
  • missed_wake_is_detected
  • missed_disconnect_is_detected
  • notify_storm_is_not_missed
• src/ownership.rs: deadline_tracks_each_state
• src/transport/unix.rs:
  • wake_is_cloexec_and_nonblocking
  • wake_notify_never_blocks_and_drain_empties
  • listener_wait_reports_each_source
  • listener_wait_rounds_timeout_up

Mutation checks

• Removing the handler-completion (Done) notify fails handler_completion_closes_socket_promptly.
• Removing the update_ownership notify fails owned_handoff_expiry_keeps_daemon.
• Making tick notify fails idle_loop_does_not_spin, missed_wake_is_detected, and missed_disconnect_is_detected.

Flakiness runs

• Server module ×10, full lib ×10, concurrent ×5, single-threaded ×3. All passed.

Validation

• cargo fmt --check and cargo clippy --locked --all-targets --all-features -- -D warnings pass (toolchain 1.90.0).
• The macOS CI test selection passes: cargo test --locked --lib --test service --test runtime --test ownership --test rows --test ghostty-effects (lib 59, ghostty-effects 5, ownership 8, rows 1, runtime 8 + 1 ignored, service 9).
• Cross clippy with -D warnings passes for x86_64-pc-windows-msvc and x86_64-unknown-linux-gnu (--all-targets --all-features, ghostty-vt link libs stubbed). Native Windows and Linux are verified by CI.