Run PR gate on main so required-checks list can discover it

.github/workflows/pr-gate.yml

@@ -1,16 +1,14 @@
-# Always runs on PRs so required status checks complete when path-filtered
-# workflows (.github/workflows/dotnet.yml, gdscript.yml) are skipped.
-# In GitHub: Settings → Rules / Branch protection → require “PR gate / build”
-# (or drop a stale required check that never runs on docs-only PRs).
+# Path-filtered CI may skip; this always runs. Push includes main so the check
+# runs on the default branch — GitHub only lists a workflow under “required status
+# checks” after it has completed on the default branch at least once.
 name: PR gate
 
 on:
   pull_request:
     branches: [main]
-  # pull_request does not run on "push branch only" — only after a PR exists (or is synced).
   push:
-    branches-ignore:
-      - main
+    branches:
+      - "**"
 
 jobs:
   build: