Run the coverage workflow on every branch

Previously only the default branch, so a coverage run existed for work
that had already landed and for nothing in progress.

Dependabot's branches stay out. GitHub treats a run it triggers as
coming from a fork and hands it Dependabot secrets rather than Actions
secrets, so `CODECOV_TOKEN` resolves empty and the upload fails; a
bump's coverage run is the one on the default branch after it merges.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: Technologicat

.github/workflows/coverage.yml

@@ -7,7 +7,11 @@ name: Coverage
 
 on:
   push:
-    branches: [ master ]
+    # Every branch, so work in progress gets the same coverage run as `master` does.
+    # Dependabot's are the exception: GitHub hands its runs Dependabot secrets rather than Actions
+    # secrets, so `CODECOV_TOKEN` would be empty and the upload would fail on every bump. A bump's
+    # coverage run is the one that happens on `master` after it merges.
+    branches-ignore: ['dependabot/**']
   workflow_dispatch:
 
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