Add mock update feed UI tests

.github/workflows/ci.yml

@@ -0,0 +1,45 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  ui-tests:
+    runs-on: self-hosted
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Select Xcode
+        run: |
+          set -euo pipefail
+          if [ -d "/Applications/Xcode.app/Contents/Developer" ]; then
+            XCODE_DIR="/Applications/Xcode.app/Contents/Developer"
+          else
+            XCODE_APP="$(ls -d /Applications/Xcode*.app 2>/dev/null | head -n 1 || true)"
+            if [ -n "$XCODE_APP" ]; then
+              XCODE_DIR="$XCODE_APP/Contents/Developer"
+            else
+              echo "No Xcode.app found under /Applications" >&2
+              exit 1
+            fi
+          fi
+          echo "DEVELOPER_DIR=$XCODE_DIR" >> "$GITHUB_ENV"
+          export DEVELOPER_DIR="$XCODE_DIR"
+          xcodebuild -version
+          xcrun --sdk macosx --show-sdk-path
+
+      - name: Run UI tests
+        run: |
+          xcodebuild \
+            -project GhosttyTabs.xcodeproj \
+            -scheme cmux \
+            -configuration Debug \
+            -destination 'platform=macOS' \
+            -only-testing:GhosttyTabsUITests/UpdatePillUITests \
+            test