ci: bump to Xcode 26.3 and fix CalendarWatcher.stop race

.github/workflows/ci.yml

@@ -8,20 +8,26 @@ on:
 
 jobs:
   test:
-    runs-on: macos-15
+    # Needs macOS 26 host: Xcode 26's `actool` invokes AVFCore-backed
+    # `ibtoold` for `.icon` asset compilation, which dyld-fails on macOS 15
+    # because of missing CoreMedia symbols (e.g. `_kFigCaptionRegionDisplayAlign_Before`).
+    # `swift build` and `swift test` worked on `macos-15` once xcode-select
+    # pointed at Xcode 26.3, but the app's asset catalog needs the OS frameworks.
+    runs-on: macos-26
     steps:
       - uses: actions/checkout@v4
       - name: Select Xcode
-        run: sudo xcode-select -s /Applications/Xcode_16.app
+        # mlx-audio-swift requires swift-tools-version:6.2 (Xcode 26).
+        run: sudo xcode-select -s /Applications/Xcode_26.3.app
       - name: Build core
         run: swift build
       - name: Test core
         run: swift test --enable-code-coverage
       - name: Build app
         run: |
           xcodebuild \
-            -project TranscriberApp/TranscriberApp.xcodeproj \
-            -scheme TranscriberApp \
+            -project TranscriberApp/Scribe.xcodeproj \
+            -scheme Scribe \
             -configuration Debug \
             -destination 'platform=macOS' \
             build \

Sources/TranscriberCore/Calendar/CalendarWatcher.swift

@@ -68,9 +68,18 @@ public actor CalendarWatcher {
         }
     }
 
-    public func stop() {
-        pollTask?.cancel()
+    /// Cancels the poll loop and awaits its termination. The previous sync
+    /// variant returned before the in-flight `refreshNow()` had finished, so
+    /// `stop()` could complete and a stale poll iteration would still bump
+    /// the lookup callout afterward — visible on slower hardware as a
+    /// flaky `testStopCancelsPollLoop`. By awaiting `task.value` here, any
+    /// in-progress refresh is allowed to drain before `stop()` returns and
+    /// no further polls can happen for this watcher instance.
+    public func stop() async {
+        let task = pollTask
         pollTask = nil
+        task?.cancel()
+        await task?.value
     }
 
     /// Forces an immediate refresh outside the regular cadence. Called on