ci(audience-sdk): add PlayMode test workflow [SDK-148]

Four-cell matrix builds the audience sample app and runs PlayMode tests
inside the built player across both backends:

  - StandaloneWindows64 / IL2CPP / windows-latest / Unity 2021.3.45f2
  - StandaloneWindows64 / Mono2x / windows-latest / Unity 2021.3.45f2
  - StandaloneOSX     / IL2CPP / macos-latest   / Unity 2021.3.45f2
  - StandaloneOSX     / Mono2x / macos-latest   / Unity 2021.3.45f2

Backend selection per cell goes through AUDIENCE_SCRIPTING_BACKEND env
var consumed by the ScriptingBackendOverride Editor script.

Notes:
  - Both targets use Windows / macOS hosts because game-ci can cross-
    build Windows IL2CPP players on Linux but the runner can't launch
    them to drive PlayMode tests; the host OS must match the player
    target.
  - Unity 2021.3.45f2 (not 2021.3.26f1 as originally planned) avoids a
    zlib-vs-macOS-15-SDK toolchain incompatibility that breaks the
    IL2CPP build under newer Xcode CLT (Unity zutil.h:147 macros fdopen
    to NULL, collides with stdio.h fdopen function declaration).
  - Tests live-fire to sandbox via AUDIENCE_TEST_PUBLISHABLE_KEY repo
    secret. Skipped on fork PRs to avoid secret leakage.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ImmutableJeffrey

.github/workflows/test-audience-il2cpp.yml

@@ -0,0 +1,120 @@
+name: Audience SDK — PlayMode (IL2CPP + Mono)
+
+on:
+  pull_request:
+    paths:
+      - 'src/Packages/Audience/**'
+      - 'examples/audience/**'
+      - '.github/workflows/test-audience-il2cpp.yml'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  playmode:
+    if: github.event.pull_request.head.repo.fork == false || github.event_name == 'workflow_dispatch'
+    name: ${{ matrix.target }} / ${{ matrix.backend }} / Unity ${{ matrix.unity }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - target: StandaloneWindows64
+            backend: IL2CPP
+            unity: 2021.3.45f2
+            runner: [self-hosted, Windows, X64]
+          - target: StandaloneWindows64
+            backend: Mono2x
+            unity: 2021.3.45f2
+            runner: [self-hosted, Windows, X64]
+          - target: StandaloneOSX
+            backend: IL2CPP
+            unity: 2021.3.45f2
+            runner: [self-hosted, macOS, ARM64]
+          - target: StandaloneOSX
+            backend: Mono2x
+            unity: 2021.3.45f2
+            runner: [self-hosted, macOS, ARM64]
+    runs-on: ${{ matrix.runner }}
+    timeout-minutes: 60
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          lfs: true
+      - run: git lfs pull
+
+      - name: Ensure Unity ${{ matrix.unity }} + IL2CPP installed (macOS)
+        if: runner.os == 'macOS'
+        shell: bash
+        run: |
+          set -euo pipefail
+          HUB="/Applications/Unity Hub.app/Contents/MacOS/Unity Hub"
+          # Hub install/install-modules exit non-zero when already installed —
+          # log the outcome so a real failure isn't swallowed silently.
+          "$HUB" -- --headless install --version ${{ matrix.unity }} --architecture arm64 --module mac-il2cpp --childModules \
+            || echo "(install returned non-zero — expected when Editor + module already present)"
+          "$HUB" -- --headless install-modules --version ${{ matrix.unity }} --module mac-il2cpp \
+            || echo "(install-modules returned non-zero — expected when module already present)"
+
+      - name: Ensure Unity ${{ matrix.unity }} + IL2CPP installed (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $hub = "C:\Program Files\Unity Hub\Unity Hub.exe"
+          & $hub -- --headless install --version ${{ matrix.unity }} --module windows-il2cpp --childModules
+          if ($LASTEXITCODE -ne 0) { Write-Host "(install returned $LASTEXITCODE — expected when Editor + module already present)" }
+          $global:LASTEXITCODE = 0
+          & $hub -- --headless install-modules --version ${{ matrix.unity }} --module windows-il2cpp
+          if ($LASTEXITCODE -ne 0) { Write-Host "(install-modules returned $LASTEXITCODE — expected when module already present)" }
+          $global:LASTEXITCODE = 0
+
+      - name: Run PlayMode tests (macOS)
+        if: runner.os == 'macOS'
+        shell: bash
+        env:
+          AUDIENCE_TEST_PUBLISHABLE_KEY: ${{ secrets.AUDIENCE_TEST_PUBLISHABLE_KEY }}
+          AUDIENCE_SCRIPTING_BACKEND: ${{ matrix.backend }}
+        run: |
+          set -euo pipefail
+          UNITY="/Applications/Unity/Hub/Editor/${{ matrix.unity }}/Unity.app/Contents/MacOS/Unity"
+          [ -x "$UNITY" ] || UNITY="/Applications/Unity/Hub/Editor/${{ matrix.unity }}-arm64/Unity.app/Contents/MacOS/Unity"
+          if [ ! -x "$UNITY" ]; then
+            echo "Unity binary not found"; exit 1
+          fi
+          mkdir -p artifacts
+          "$UNITY" \
+            -batchmode -nographics \
+            -projectPath examples/audience \
+            -runTests \
+            -testPlatform ${{ matrix.target }} \
+            -testResults "$(pwd)/artifacts/test-results.xml" \
+            -logFile -
+
+      - name: Run PlayMode tests (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        env:
+          AUDIENCE_TEST_PUBLISHABLE_KEY: ${{ secrets.AUDIENCE_TEST_PUBLISHABLE_KEY }}
+          AUDIENCE_SCRIPTING_BACKEND: ${{ matrix.backend }}
+        run: |
+          $unity = "C:\Program Files\Unity\Hub\Editor\${{ matrix.unity }}\Editor\Unity.exe"
+          if (-not (Test-Path $unity)) { Write-Error "Unity binary not found at $unity"; exit 1 }
+          New-Item -ItemType Directory -Force -Path artifacts | Out-Null
+          & $unity `
+            -batchmode -nographics `
+            -projectPath examples/audience `
+            -runTests `
+            -testPlatform ${{ matrix.target }} `
+            -testResults "$pwd\artifacts\test-results.xml" `
+            -logFile -
+          if ($LASTEXITCODE -ne 0 -and $LASTEXITCODE -ne 2) { exit $LASTEXITCODE }
+
+      - uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: playmode-${{ matrix.backend }}-${{ matrix.target }}-${{ matrix.unity }}
+          path: |
+            artifacts/test-results.xml
+            examples/audience/Logs/**