feat(apple): iOS/iPadOS client — touch, pointer lock, shared SwiftUI shell

The whole client now runs on iPadOS/iOS from the same sources, first-lit live in the
iPad simulator against the real host at 1280x720@60 (60 fps on the HUD, capture state
machine active, mic permission flow shown).

- PunktfunkCore.xcframework grows iOS device + universal-simulator slices
  (BUILD_IOS=1; rustup targets aarch64-apple-ios{,-sim} + x86_64-apple-ios).
- The decode pump is extracted into a shared StreamPump (identical IDR re-gate logic on
  both platforms); the iOS StreamView (StreamViewIOS.swift) has the same name/signature
  as the macOS one, so ContentView & co. are byte-identical across platforms — hosted
  in a UIViewController for prefersPointerLocked (the iPadOS cursor capture; see README
  note 9 for the UIHostingController forwarding caveat).
- Touch is always forwarded: per-finger wire ids, coordinates mapped through the
  aspect-fit letterbox into LIVE host-mode pixels (surface == host mode, identity
  rescale host-side; follows mid-stream requestMode switches).
- InputCapture is cross-platform: GC works the same on iPadOS, ⌘⎋ is detected from the
  HID stream there; stale-⌘ tracking after focus loss fixed on both platforms
  (releaseAll now drops the modifier/latch state — a ⌘ released in another app
  otherwise hijacked Esc forever).
- SessionAudio: AVAudioSession on iOS (.playAndRecord + .defaultToSpeaker — without it
  iPhones route host audio to the EARPIECE; deactivated with
  notifyOthersOnDeactivation on stop so interrupted background audio resumes); HAL
  device pinning + the Settings pickers stay macOS-only.
- New Punktfunk-iOS app target (shared synchronized sources, generated Info.plist with
  mic + local-network usage descriptions — QUIC to a LAN host trips local network
  privacy on real devices — scene manifest + indirect input events for Stage Manager /
  external displays), shared scheme, macOS min-window frames gated off iOS.

For the iPad-on-an-external-screen idea: with multiple scenes + indirect input enabled,
Stage Manager iPads can drag the punktfunk window onto the external display and drive
the PC with keyboard/mouse/touch. Known gaps (README note 9): the pointer-lock
preference isn't consulted through UIHostingController (relative mouse works, the local
cursor just stays visible) and AVAudioSession interruptions don't auto-restart audio.

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

scripts/build-xcframework.sh

@@ -11,7 +11,7 @@ set -euo pipefail
 cd "$(dirname "$0")/.."
 
 TARGETS_MAC=(aarch64-apple-darwin x86_64-apple-darwin)
-BUILD_IOS="${BUILD_IOS:-0}" # BUILD_IOS=1 adds an iOS slice (requires the ios target installed)
+BUILD_IOS="${BUILD_IOS:-0}" # BUILD_IOS=1 adds iOS device + simulator slices (rustup targets aarch64-apple-ios{,-sim})
 
 # Deployment targets must match Package.swift's platforms, or every consumer link emits
 # "object file was built for newer macOS version" warnings.
@@ -20,6 +20,8 @@ for t in "${TARGETS_MAC[@]}"; do
 done
 if [[ "$BUILD_IOS" == "1" ]]; then
     IPHONEOS_DEPLOYMENT_TARGET=17.0 cargo build --release -p punktfunk-core --features quic --target aarch64-apple-ios
+    IPHONEOS_DEPLOYMENT_TARGET=17.0 cargo build --release -p punktfunk-core --features quic --target aarch64-apple-ios-sim
+    IPHONEOS_DEPLOYMENT_TARGET=17.0 cargo build --release -p punktfunk-core --features quic --target x86_64-apple-ios
 fi
 
 STAGE="$(mktemp -d)"
@@ -48,7 +50,14 @@ EOF
 
 ARGS=(-library "$STAGE/macos/libpunktfunk_core.a" -headers "$STAGE/include")
 if [[ "$BUILD_IOS" == "1" ]]; then
+    # Universal simulator lib (arm64 Macs run arm64 sims, but generic builds link x86_64 too).
+    mkdir -p "$STAGE/iossim"
+    lipo -create \
+        target/aarch64-apple-ios-sim/release/libpunktfunk_core.a \
+        target/x86_64-apple-ios/release/libpunktfunk_core.a \
+        -output "$STAGE/iossim/libpunktfunk_core.a"
     ARGS+=(-library target/aarch64-apple-ios/release/libpunktfunk_core.a -headers "$STAGE/include")
+    ARGS+=(-library "$STAGE/iossim/libpunktfunk_core.a" -headers "$STAGE/include")
 fi
 
 # Cargo does NOT fingerprint MACOSX_DEPLOYMENT_TARGET — units cached from a build without