Fix display resolution UI test foreground activation on CI

XCUIApplication.launch() fails to activate the app on headless CI
runners, reporting "Failed to activate application (current state:
Running Background)". With continueAfterFailure=false, this kills the
test before ensureForegroundAfterLaunch can retry.

Fix by temporarily setting continueAfterFailure=true around launch(),
then retrying activation via app.activate(). Also add a retry loop in
the CI workflow since foreground activation is inherently flaky on
headless runners.

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

.github/workflows/ci.yml

@@ -495,12 +495,24 @@ jobs:
           {"helperBinaryPath":"$HELPER_PATH"}
           EOF
 
-          xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
+          # Retry once — foreground activation on headless CI runners is flaky
+          for attempt in 1 2; do
+            if xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
               -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
               -disableAutomaticPackageResolution \
               -destination "platform=macOS" \
               -only-testing:cmuxUITests/DisplayResolutionRegressionUITests \
-            test
+              test; then
+              exit 0
+            fi
+            if [ "$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: |

cmuxUITests/DisplayResolutionRegressionUITests.swift

@@ -244,9 +244,21 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
         for (key, value) in launchEnvironment(targetDisplayID: targetDisplayID) {
             app.launchEnvironment[key] = value
         }
+
+        // On headless CI runners, XCUIApplication.launch() may fail to activate
+        // the app (reporting "Failed to activate application" as a test error).
+        // Temporarily allow continuation so we can retry activation manually.
+        continueAfterFailure = true
         app.launch()
+        continueAfterFailure = false
         launchedApp = app
 
+        guard ensureForegroundAfterLaunch(app, timeout: 15.0) else {
+            throw NSError(domain: "DisplayResolutionRegressionUITests", code: 2, userInfo: [
+                NSLocalizedDescriptionKey: "App failed to reach foreground. state=\(app.state.rawValue) diagnostics=\(loadDiagnostics() ?? [:])"
+            ])
+        }
+
         if !waitForAppLaunchDiagnostics(timeout: 12.0) {
             throw NSError(domain: "DisplayResolutionRegressionUITests", code: 2, userInfo: [
                 NSLocalizedDescriptionKey: "App failed to write launch diagnostics. state=\(app.state.rawValue) diagnostics=\(loadDiagnostics() ?? [:])"
@@ -254,6 +266,17 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
         }
     }
 
+    private func ensureForegroundAfterLaunch(_ app: XCUIApplication, timeout: TimeInterval) -> Bool {
+        if app.wait(for: .runningForeground, timeout: timeout) {
+            return true
+        }
+        if app.state == .runningBackground {
+            app.activate()
+            return app.wait(for: .runningForeground, timeout: 6.0)
+        }
+        return false
+    }
+
     private func launchEnvironment(targetDisplayID: String) -> [String: String] {
         [
             "CMUX_UI_TEST_MODE": "1",