build: switch to macos "large" to fix missing Firefox

The Arm64 images have been catered to Google and its Chrome browser
only, omitting Firefox.

Ref actions/runner-images#9974

.github/workflows/CI.yaml

@@ -27,9 +27,9 @@ jobs:
             node: 20.x
 
           # Includes Firefox, Google Chrome, Safari
-          # https://github.com/actions/runner-images/blob/macos-15/20241217.493/images/macos/macos-15-Readme.md
+          # https://github.com/actions/runner-images/blob/macos-14/20241216.504/images/macos/macos-14-Readme.md
           - name: "macOS: Node 20"
-            os: macos-15
+            os: macos-14-large
             node: 20.x
 
     name: ${{ matrix.name }}

src/browsers.js

@@ -236,7 +236,20 @@ class FirefoxBrowser {
     try {
       await LocalBrowser.spawn(this.getCandidates(), args, signal, logger);
     } finally {
-      fs.rmSync(profileDir, { recursive: true, force: true });
+      // On Windows, when spawn() returns after firefox.exe has stopped, it sometimes can't delete
+      // some temporary files yet as they're somehow still in use (EBUSY). Perhaps a race condition,
+      // or an lagged background process?
+      // > BUSY: resource busy or locked,
+      // > unlink 'C:\Users\RUNNER~1\AppData\Local\Temp\qtap_EZ4IoO\bounce-tracking-protection.sqlite'
+      // Enable `maxRetries` to cover the common case, and beyond that try-catch
+      // as it is not critical for test completion.
+      // TODO: Can we abstract this so that it happens automatically for any directory
+      // obtained via LocalBrowser.makeTempDir?
+      try {
+        fs.rmSync(profileDir, { recursive: true, force: true, maxRetries: 2 });
+      } catch (e) {
+        logger.warning('firefox_cleanup_fail', e);
+      }
     }
   }
 }

src/qtap.js

@@ -87,6 +87,12 @@ async function run (browserNames, files, options) {
     // exits naturally by itself.
     // TODO: Consider just calling process.exit after this await.
     // Is that faster and safe? What if any important clean up would we miss?
+    // 1. Removing of temp directories is generally done in browser "launch" functions
+    //    after the child process has properly ended (and has to, as otherwise the
+    //    files are likely still locked and/or may end up re-created). If we were to
+    //    exit earlier, we may leave temp directories behind. This is fine when running
+    //    in an ephemeral environment (e.g. CI), but not great for local dev.
+    //
     await Promise.allSettled(browserLaunches);
     // Await again, so that any error gets thrown accordingly,
     // we don't do this directly because we first want to wait for all tests