fix(apple): scroll from trackpads/Magic Mouse — forward NSEvent scrollWheel, drop GC scroll

Scroll was wired to GCMouse's scroll dpad, which only fires for plain HID wheel
deltas — trackpad and Magic Mouse scrolling are gesture events that never reach
GameController, so scrolling was dead on the default Mac setups. The stream view now
overrides scrollWheel (while captured the cursor is parked mid-view, so it receives
every scroll event) and feeds InputCapture.sendScroll: precise gesture deltas are
pixels (~0.1 notch/px, SDL's factor → ×12 for WHEEL_DELTA(120)), classic wheels are
lines (×120), fractional remainders accumulate, and the GC scroll handler is gone so
wheel mice can't double-deliver. Signs pass through as-is, preserving the local
(natural-)scrolling preference.

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

clients/apple/README.md

@@ -37,8 +37,9 @@ What's here, all compiled and tested on macOS (Xcode 26.5 / Swift 6.3):
     thread per view, token-cancelled so reconnects can't double-pump.
   - `InputCapture.swift` — `GCMouse` raw deltas + `GCKeyboard` HID→VK mapping (the host's
     `vk_to_evdev` consumes Windows VKs), with fractional-delta accumulation so sub-pixel
-    motion isn't truncated away. Buttons use GameStream ids (1=left … 5=X2); scroll is
-    WHEEL_DELTA(120)-scaled.
+    motion isn't truncated away. Buttons use GameStream ids (1=left … 5=X2). Scroll
+    arrives via the stream view's `scrollWheel` override instead of GC (trackpad/Magic
+    Mouse gestures never reach GCMouse's scroll dpad), WHEEL_DELTA(120)-scaled.
 - **`PunktfunkClient`** (the app): hosts grid (saved in UserDefaults), "+" toolbar
   sheet to add hosts, stream mode in Settings (⌘,), two trust flows — the
   trust-on-first-use fingerprint prompt over the live-but-blurred stream, and SPAKE2 PIN