MIDI clock sync + note output over USB/BLE (v0.18.0)

Add a MIDI Sync settings card (before the binding cards) with Send and Receive
MIDI clock toggles, both off by default and persisted.

Send: a dedicated thread emits clock (0xF8) at 24 PPQN plus Start/Stop on the
transport edges to every attached MIDI device (USB + Bluetooth), and — because a
sequencer should drive gear, not just its tempo — also forwards the tracks'
note-on/off on each cell's MIDI channel. Notes are queued from the audio thread
through a lock-free ring and drained by the send thread, mirroring the mono-per-
track cell lifecycle; stop/pause/panic release everything so external notes never
hang. (Per-channel Arpeggiator/Transposer are internal FX and aren't reflected.)

Receive: MidiInput now forwards real-time bytes to the clock module, which follows
an external clock — Start/Continue starts the transport, Stop pauses it, and the
pulse rate drives the tempo (a tempo + transport follow, not a sample-locked slave).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/space/rcmd/android/sizzle/SizzleApp.kt

@@ -45,6 +45,11 @@ class SizzleApp : Application() {
     val gamepadInput: GamepadInput by lazy { GamepadInput(inputRouter) }
     val midiInput: MidiInput by lazy { MidiInput(this, inputRouter) }
 
+    /** MIDI clock sync (send/receive) over USB + Bluetooth MIDI. */
+    val midiClock: space.rcmd.android.sizzle.input.MidiClock by lazy {
+        space.rcmd.android.sizzle.input.MidiClock(this)
+    }
+
     /** Persists the input binding maps across restarts (DataStore-backed). */
     val bindingStore: BindingStore by lazy { BindingStore(this) }
 
@@ -80,6 +85,8 @@ class SizzleApp : Application() {
         // single small read; blocking briefly at cold start keeps the input maps
         // authoritative from the first keypress rather than racing an async load.
         runBlocking { bindingStore.loadInto(keyboardInput, gamepadInput, midiInput) }
+        // Feed incoming MIDI real-time (clock / start / stop) to the clock sync module.
+        midiInput.onRealtime = midiClock::handleRealtime
         installCrashAutosave()
     }