feat(capture): swap the rdev fork for keytap 0.2, delete local chord state machine

Dep swap:
- Drop the git-pinned jamiepine/rdev fork we were carrying since the
  upstream crate is abandoned.
- Depend on keytap 0.2 from crates.io — our own cross-platform global
  keyboard tap crate. Clean shutdown via Drop, Sonoma-safe by design
  (no TSMGetInputSourceProperty calls off the main thread, so
  `set_is_main_thread(false)` is gone), and properly versioned.

Chord engine rewrite:
- Delete hotkey_monitor.rs's internal Chord state machine (Match enum,
  KeyEvent enum, step()/classify() methods, associated unit tests).
  keytap's ChordMatcher subsumes it: Momentary chord for PTT,
  add_toggle() for Toggle-to-talk, longest-match resolution, sticky-end
  for Toggle. Net: -80 LOC in hotkey_monitor.rs; the remaining module
  is the dispatcher loop + Effect→Tauri translation.
- Preserve the PTT→Toggle "RestartRecording" upgrade signal. keytap
  emits End(PTT)+Start(Toggle) atomically (same Instant) when the held
  set upgrades from a shorter chord to a longer superset. The
  dispatcher peeks at the matcher with a 5 ms recv_timeout after any
  End and coalesces the pair into Effect::RestartRecording so the
  frontend still gets the "discard the transition-moment audio" signal
  instead of an unrelated Stop+Start pair.
- HotkeyMonitor::update_bindings now actually tears down the tap on
  empty bindings instead of leaving an idle CGEventTap around. New
  bindings rebuild the matcher and the dispatcher thread from scratch.

key_codes.rs:
- Rewrite the browser-code → Key table against keytap's cleaner Key
  variant names (`A`..`Z` not `KeyA`..`KeyZ`, `Digit0`..`Digit9` not
  `Num0`..`Num9`, `ArrowUp` not `UpArrow`, `AltLeft`/`AltRight` instead
  of `Alt`/`AltGr`, `Period` not `Dot`, …). On-disk chord string
  format (W3C `KeyboardEvent.code` identifiers) is unchanged, so
  capture_settings rows written before the swap round-trip identically.
  Legacy aliases (`Alt`, `AltGr`, `Num0`, `UpArrow`, `Dot`, …) kept for
  forward-compat on old rows.

main.rs / input_monitoring.rs:
- Update the few doc comments that referenced `rdev::listen` to
  describe keytap's Tap; no behavioural change.
- build_chord_bindings now imports from keytap::Key.
- enable_hotkey / disable_hotkey / update_chord_bindings reach into
  HotkeyMonitor via &mut since apply()/update_bindings() now mutate.

Tests live in keytap now (22 chord-related tests in keytap 0.2,
including the PTT→Toggle upgrade scenario that used to be tested in
hotkey_monitor.rs). Voicebox's hotkey_monitor.rs is thin enough that
local testing would be trivia.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

tauri/src-tauri/Cargo.toml

@@ -52,19 +52,15 @@ webkit2gtk = "2.0"
 [target.'cfg(not(any(target_os = "android", target_os = "ios")))'.dependencies]
 tauri-plugin-updater = "2.0"
 tauri-plugin-process = "2.0"
-# Pinned to our fork of upstream main past PR #147 — the released 0.5.3
-# crate crashes on macOS 14+ when listen() runs on a background thread
-# because rdev's convert() calls TSMGetInputSourceProperty off the main
-# queue. The main branch adds `set_is_main_thread(false)` to skip that
-# path (used at hotkey_monitor.rs:184).
-#
-# We pin to jamiepine/rdev instead of Narsil/rdev for supply-chain
-# durability: upstream has shipped no release since 2023-06 (crates.io
-# still lists 0.5.3), so an eventual 0.5.4 carrying this fix is unlikely,
-# and a git pin to a third-party repo breaks if the remote force-pushes,
-# renames, or disappears. The fork mirrors the pinned SHA and gives us a
-# place to cherry-pick future OS-compatibility fixes on our own timeline.
-rdev = { git = "https://github.com/jamiepine/rdev", rev = "c14f2dc5c8100a96c5d7e3013de59d6aa0b9eae2" }
+# Observe-only global keyboard tap. Covers macOS, Windows, and Linux
+# (evdev) with left/right modifier fidelity, which is the hard
+# requirement the chord engine needs. keytap is our own crate
+# (jamiepine/keytap), published to crates.io, that replaces the
+# abandoned Narsil/rdev we previously pinned via git — same capability
+# surface, clean shutdown via Drop, no `set_is_main_thread(false)`
+# dance required (the Sonoma-crashing layout-translation path simply
+# isn't called).
+keytap = "0.2"
 
 [features]
 # This feature is used for production builds or when `devPath` points to the filesystem