fix: address Copilot review comments

- service_worker.js: wrap skipWaiting() in event.waitUntil() so the
  install event cannot complete before skipWaiting resolves
- firefox_version.py: use re.subn() and raise if no TAG line matched,
  preventing silent no-op updates if install-firefox.sh format changes
- docs/Release-Checklist.md: replace manual Firefox-tag step and stale
  update.sh reference with the new update.py / firefox_version.py workflow

Author: vringar

docs/Release-Checklist.md

@@ -2,12 +2,13 @@
 
 We aim to release a new version of OpenWPM with each new Firefox release (~1 release per month). The following steps are necessary for a release:
 
-1. Upgrade Firefox to the newest version.
-    1. Go to: <https://hg.mozilla.org/releases/mozilla-release/tags>.
-    2. Find the commit hash for the Firefox release version you'd like to upgrade to.
-    3. Update the `TAG` variable in [`scripts/install-firefox.sh`](../scripts/install-firefox.sh#L12) to that hash and the comment to the new tag name.
+1. Run `python scripts/update.py` — this will:
+    - Repin the conda environment
+    - Bump all npm dependencies to their latest compatible versions
+    - Rebuild the extension
+    - Automatically detect and apply any new Firefox release to `scripts/install-firefox.sh`
 2. Check if we can unpin our python version (this requires Linux to test) See <https://github.com/openwpm/OpenWPM/issues/1111>
-3. Run `./scripts/update.sh`
+3. Run `./scripts/install-firefox.sh` to install the updated Firefox locally and verify the test suite passes.
 4. Increment the version number in [VERSION](../VERSION)
 5. Add a summary of changes since the last version to [CHANGELOG](../CHANGELOG.md)
 6. Squash and merge the release PR to master.

scripts/firefox_version.py

@@ -66,12 +66,16 @@ def update_if_needed() -> bool:
 
     print(f"Updating Firefox: {current} → {latest_tag}")
     text = INSTALL_SCRIPT.read_text()
-    new_text = re.sub(
+    new_text, count = re.subn(
         r"^TAG='[^']*' # .*$",
         f"TAG='{latest_hash}' # {latest_tag}",
         text,
         flags=re.MULTILINE,
     )
+    if count == 0:
+        raise RuntimeError(
+            f"Failed to update TAG line in {INSTALL_SCRIPT}: no matching line found"
+        )
     INSTALL_SCRIPT.write_text(new_text)
     print(f"Updated {INSTALL_SCRIPT.name} to {latest_tag} ({latest_hash})")
     print("Remember to run ./scripts/install-firefox.sh and test before releasing.")

test/test_pages/shared/service_worker.js

@@ -2,7 +2,7 @@ var IMAGE_URL = 'http://localhost:8000/test_pages/shared/test_image_2.png';
 
 self.addEventListener('install', function(event) {
   // Skip the waiting phase so this worker activates immediately after install.
-  self.skipWaiting();
+  event.waitUntil(self.skipWaiting());
 });
 
 self.addEventListener('activate', function(event) {