Use NSWorkspace to launch app in display resolution UI test

XCUIApplication.launch() hard-fails with a 60-second timeout when
it can't foreground the app on headless CI runners. This test never
uses XCUIApplication for interaction (no taps/keys) — it only reads
a diagnostics file.

Replace with NSWorkspace.openApplication which launches through
Launch Services, passes env vars via OpenConfiguration, and returns
immediately without blocking on activation failure.

Also add CI retry loop since runner environment is flaky.

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

.github/workflows/ci.yml

@@ -495,12 +495,23 @@ jobs:
           {"helperBinaryPath":"$HELPER_PATH"}
           EOF
 
-          xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
-            -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
-            -disableAutomaticPackageResolution \
-            -destination "platform=macOS" \
-            -only-testing:cmuxUITests/DisplayResolutionRegressionUITests \
-            test
+          for attempt in 1 2; do
+            if xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
+              -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
+              -disableAutomaticPackageResolution \
+              -destination "platform=macOS" \
+              -only-testing:cmuxUITests/DisplayResolutionRegressionUITests \
+              test; then
+              exit 0
+            fi
+            if [ "$attempt" -eq 2 ]; then
+              echo "Display resolution UI regression failed after 2 attempts" >&2
+              exit 1
+            fi
+            echo "Attempt $attempt failed, retrying..."
+            pkill -x "cmux DEV" 2>/dev/null || true
+            sleep 3
+          done
 
       - name: Run browser find focus UI regression
         run: |