fix: use correct checkout SHA and simplify CI workflow

The previous checkout SHA was invalid, causing immediate CI failure.
Use the known-good actions/checkout v4.2.2 SHA. Simplify trigger to
on: [push] to match other repos. Keep --ulimit memlock=-1:-1 for
10MB secret tests that need mlock.

.gitea/workflows/check.yml

@@ -1,16 +1,9 @@
-name: Check
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-
+name: check
+on: [push]
 jobs:
-  check:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13925f8d5 # v4
-
-      - name: Build (includes make check)
-        run: docker build --ulimit memlock=-1:-1 .
+    check:
+        runs-on: ubuntu-latest
+        steps:
+            # actions/checkout v4.2.2, 2026-02-28
+            - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+            - run: docker build --ulimit memlock=-1:-1 .