fix(apple): resolve macOS modifiers by keyCode — Control was silently dropped

Modifier keys arrive only as flagsChanged, and the direction was recovered
by diffing the device-dependent L/R bits (NX_DEVICE*KEYMASK) alone. Those
bits are undocumented and some keyboards omit them (only the class bit,
e.g. NX_CONTROLMASK, is set), so the diff saw no transition and the key
never reached the host — no Ctrl shortcuts. SDL/Moonlight key off the
event's keyCode for exactly this reason; do the same: keyCode names the
changed key, the class bit says up, the device bits (when present) pick
the side, and a tracked-held-state flip covers keyboards without them.

PUNKTFUNK_INPUT_DEBUG=1 now also logs every flagsChanged (keyCode + raw
flags) so a field report is diagnosable from client logs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkKit/Views/StreamView.swift

@@ -346,10 +346,13 @@ public final class StreamLayerView: NSView {
         super.keyUp(with: event)
     }
     /// Modifier keys (shift/control/option/command) arrive ONLY as flagsChanged on macOS,
-    /// never keyDown/keyUp — InputCapture diffs the raw flags to recover each L/R down/up.
+    /// never keyDown/keyUp — the changed key is `event.keyCode`; InputCapture resolves the
+    /// down-vs-up direction from the flags (diffing the device-dependent flag bits alone
+    /// proved unreliable — some keyboards omit them, which silently dropped Control).
     public override func flagsChanged(with event: NSEvent) {
         if captured, let inputCapture {
-            inputCapture.handleFlagsChanged(UInt(event.modifierFlags.rawValue))
+            inputCapture.handleFlagsChanged(
+                keyCode: event.keyCode, rawFlags: UInt(event.modifierFlags.rawValue))
             return
         }
         super.flagsChanged(with: event)