Fail hung CI jobs fast with a 15-minute timeout

Two app-test jobs hung intermittently (40+ minutes against a normal
~4-5), holding macOS runners against GitHub's 360-minute default and
starving the queue - subsequent runs sat pending, which read as "CI now
takes 10+ minutes". Jobs now time out at 15 minutes (3x the normal
duration) so a hang fails loudly instead of silently consuming the
runner pool. The intermittent hang itself is under investigation
separately.

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

.github/workflows/swift-tests.yml

@@ -10,6 +10,9 @@ jobs:
   test:
     name: Run Swift Tests (${{ matrix.name }})
     runs-on: macos-latest
+    # A hung test must fail fast, not hold a runner for GitHub's 360-minute
+    # default (observed: intermittent app-suite hangs starving the queue).
+    timeout-minutes: 15
 
     strategy:
       fail-fast: false # Don't cancel other matrix jobs when one fails
@@ -76,6 +79,7 @@ jobs:
   ios-build:
     name: Build iOS app (simulator)
     runs-on: macos-latest
+    timeout-minutes: 15
 
     steps:
       - name: Checkout code