fix(ci): run CI when pull requests retarget main

.github/workflows/ci.yml

@@ -20,12 +20,15 @@ name: CI
 on:
   pull_request:
     branches: [main]
+    types: [opened, synchronize, reopened, edited]
   push:
     branches: [main]
   workflow_dispatch:
 
 concurrency:
-  group: ci-${{ github.workflow }}-${{ github.ref }}
+  # `edited` also covers title and body changes. Isolate those no-op runs so
+  # they cannot cancel the check for the current pull request revision.
+  group: ci-${{ github.workflow }}-${{ github.ref }}${{ github.event.action == 'edited' && github.event.changes.base.ref.from == '' && format('-ignored-{0}', github.run_id) || '' }}
   cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 permissions:
@@ -35,6 +38,10 @@ jobs:
   # Planning and every selected Linux surface share one runner, so the core
   # workflow consumes one automatic job without dropping affected coverage.
   test:
+    # A base-ref edit keeps the protected `CI / test` name. Other edits create
+    # only a differently named skipped check, so they cannot satisfy it.
+    name: ${{ github.event_name == 'pull_request' && github.event.action == 'edited' && github.event.changes.base.ref.from == '' && 'ignored-edit' || 'test' }}
+    if: ${{ github.event_name != 'pull_request' || github.event.action != 'edited' || github.event.changes.base.ref.from != '' }}
     runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:

scripts/ci-test-plan.test.mjs

@@ -279,6 +279,25 @@ test('core CI validates pull requests and the resulting main branch state', () =
   assert.match(workflow, /\[\[ "\$BASE_SHA" =~ \^0\+\$ \]\]/u);
 });
 
+test('core CI runs on base retargets without letting metadata edits replace the required check', () => {
+  const workflow = readWorkflow('ci.yml');
+
+  assert.match(workflow, /types: \[opened, synchronize, reopened, edited\]/u);
+  assert.match(
+    workflow,
+    /group: ci-\$\{\{ github\.workflow \}\}-\$\{\{ github\.ref \}\}\$\{\{ github\.event\.action == 'edited' && github\.event\.changes\.base\.ref\.from == '' && format\('-ignored-\{0\}', github\.run_id\) \|\| '' \}\}/u,
+  );
+  assert.match(workflow, /cancel-in-progress: \$\{\{ github\.event_name == 'pull_request' \}\}/u);
+  assert.match(
+    workflow,
+    /name: \$\{\{ github\.event_name == 'pull_request' && github\.event\.action == 'edited' && github\.event\.changes\.base\.ref\.from == '' && 'ignored-edit' \|\| 'test' \}\}/u,
+  );
+  assert.match(
+    workflow,
+    /if: \$\{\{ github\.event_name != 'pull_request' \|\| github\.event\.action != 'edited' \|\| github\.event\.changes\.base\.ref\.from != '' \}\}/u,
+  );
+});
+
 test('core CI uses the Windows inventory package-script authority', () => {
   const workflow = readWorkflow('ci.yml');