fix(ci): unbreak the Apple + Windows-client builds after the surround-audio merge

The 5.1/7.1 surround commit (75627c8) added in-core Opus, which broke two CI jobs
that the merge didn't touch:

  * Windows MSIX client: clients/windows/src/main.rs's headless `SessionParams`
    initializer was missing the new `audio_channels` field (the GUI path sets it
    from settings). Default the CLI/test path to stereo (2), matching trust.rs.
  * Apple xcframework (apple.yml + release.yml): in-core Opus decode pulls
    `audiopus_sys`, which builds a vendored *static* libopus via CMake when
    pkg-config finds no system Opus — keeping the xcframework self-contained (no
    runtime libopus.dylib on end-user Macs/devices). The self-hosted macOS runner
    lacked `cmake`; install it self-healing before every xcframework build.

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

.gitea/workflows/apple.yml

@@ -32,6 +32,13 @@ jobs:
           dirname "$RUSTUP" >> "$GITHUB_PATH"
           "$RUSTUP" target add aarch64-apple-darwin x86_64-apple-darwin
 
+      # `punktfunk-core` now decodes Opus in-core for the Apple client (surround), pulling
+      # `audiopus_sys`, which builds a vendored static libopus via CMake when pkg-config can't find a
+      # system Opus — so the xcframework is self-contained (no runtime libopus.dylib on end-user Macs).
+      # CMake must be on PATH; install it self-healing on a fresh runner.
+      - name: CMake (for the vendored libopus audiopus_sys builds)
+        run: command -v cmake >/dev/null || brew install cmake
+
       - name: Build PunktfunkCore.xcframework
         run: bash scripts/build-xcframework.sh
 
@@ -71,6 +78,10 @@ jobs:
           "$RUSTUP" target add aarch64-apple-darwin x86_64-apple-darwin \
             aarch64-apple-ios aarch64-apple-ios-sim x86_64-apple-ios
 
+      # See the swift job: audiopus_sys (via the in-core Opus decode) builds vendored libopus with CMake.
+      - name: CMake (for the vendored libopus audiopus_sys builds)
+        run: command -v cmake >/dev/null || brew install cmake
+
       - name: Build PunktfunkCore.xcframework (mac + iOS slices)
         run: BUILD_IOS=1 bash scripts/build-xcframework.sh
 

.gitea/workflows/release.yml

@@ -118,6 +118,11 @@ jobs:
           "$RUSTUP" toolchain install nightly --profile minimal
           "$RUSTUP" component add rust-src --toolchain nightly
 
+      # The in-core Opus decode (surround) pulls audiopus_sys, which builds a vendored static libopus
+      # via CMake — keep the xcframework self-contained (no runtime libopus.dylib on end-user devices).
+      - name: CMake (for the vendored libopus audiopus_sys builds)
+        run: command -v cmake >/dev/null || brew install cmake
+
       - name: Build PunktfunkCore.xcframework (mac + iOS + tvOS)
         # tvOS is a tier-3 target (nightly -Zbuild-std): slow on the first build, then cached on
         # the self-hosted runner. Built on canary too so the tvOS archive/upload below runs on the