ci: use step-level continue-on-error for macOS builds

GitHub deprecated external check run conclusion updates (Feb 2025),
so the Checks API approach to mark builds as neutral no longer works.

Instead, move continue-on-error from the job level to the build step.
The job always succeeds (green check), failed builds emit a warning
annotation, and upload is skipped on failure.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/build-tests-mac.yml

@@ -8,14 +8,10 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
   cancel-in-progress: true
 
-permissions:
-  checks: write
-
 jobs:
   buildForAllPlatformsMacOS:
     name: ${{ matrix.targetPlatform }} on ${{ matrix.unityVersion }}
     runs-on: macos-latest
-    continue-on-error: true
     strategy:
       fail-fast: false
       matrix:
@@ -66,6 +62,8 @@ jobs:
       #          Build          #
       ###########################
       - uses: ./
+        id: build
+        continue-on-error: true
         env:
           UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
           UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
@@ -81,43 +79,16 @@ jobs:
           # We use dirty build because we are replacing the default project settings file above
           allowDirtyBuild: true
 
+      - name: Warn on build failure
+        if: steps.build.outcome == 'failure'
+        run: echo "::warning::Build failed for ${{ matrix.targetPlatform }} on ${{ matrix.unityVersion }} (macOS builds are unstable)"
+
       ###########################
       #          Upload         #
       ###########################
       - uses: actions/upload-artifact@v4
+        if: steps.build.outcome == 'success'
         with:
           name: Build ${{ matrix.targetPlatform }} on MacOS (${{ matrix.unityVersion }})${{ matrix.buildProfile && '  With Build Profile' || '' }}
           path: build
           retention-days: 14
-
-  markUnstableBuilds:
-    name: Mark unstable macOS builds
-    needs: buildForAllPlatformsMacOS
-    if: always()
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/github-script@v7
-        with:
-          script: |
-            const { data: checkRuns } = await github.rest.checks.listForRef({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              ref: context.sha,
-              per_page: 100,
-            });
-
-            for (const run of checkRuns.check_runs) {
-              if (run.conclusion !== 'failure' || run.app?.slug !== 'github-actions') continue;
-              if (!run.name.includes('StandaloneOSX') && !run.name.includes('iOS')) continue;
-
-              await github.rest.checks.update({
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                check_run_id: run.id,
-                conclusion: 'neutral',
-                output: {
-                  title: `${run.name} (unstable)`,
-                  summary: 'This macOS build is unstable and its failure does not block merging.',
-                },
-              });
-            }