fix(#2097): scope QA notify workflow to default branch

.github/workflows/notify-qa.yml.template

@@ -2,6 +2,16 @@
 name: Notify tutorials-qa
 on:
   push:
+    # -Contribution repos are a MIXTURE of default branches: most default to
+    # `main`, but Tutorials-Contribution still defaults to `master`. List BOTH
+    # so this fires ONLY on the repo's default branch — and NEVER on feature
+    # branches. Without this filter a push to any branch (e.g. the devtoberfest
+    # validation-tutorial bot's `validation-tutorial/*` branches) dispatches a
+    # QA rebuild for a slug that exists only on that branch; QA discovery reads
+    # the default branch, so the slug is a phantom and the rebuild hard-fails
+    # "unknown slug in filter" (tutorials-ims#2097). Mirrors the branch filter
+    # in docs/authors/tutorial-repo-dispatch.yml (the PROD notify template).
+    branches: [master, main]
     paths:
       - 'tutorials/**'
 
@@ -17,8 +27,15 @@ jobs:
           changed=$(git diff --name-only ${{ github.event.before }} ${{ github.sha }} \
             | awk -F/ '/^tutorials\//{print $2}' | sort -u)
           count=$(echo "$changed" | wc -l)
+          # Only emit a slug when EXACTLY one tutorial changed AND it matches the
+          # strict slug charset (whole-value POSIX case match); anything else →
+          # empty slug → rebuild-content-qa.yml runs a full rebuild. Mirrors
+          # docs/authors/tutorial-repo-dispatch.yml.
           if [ "$count" = "1" ] && [ -n "$changed" ]; then
-            echo "slug=$changed" >> "$GITHUB_OUTPUT"
+            case "$changed" in
+              *[!a-z0-9-]* | -* ) echo "slug=" >> "$GITHUB_OUTPUT" ;;
+              *) echo "slug=$changed" >> "$GITHUB_OUTPUT" ;;
+            esac
           else
             echo "slug=" >> "$GITHUB_OUTPUT"
           fi

test/unit/install-notify-workflows.test.ts

@@ -392,3 +392,30 @@ describe('PROD notify template branch trigger (regression guard)', () => {
     expect(template).not.toMatch(/branches:\s*\[\s*main\s*\]/)
   })
 })
+
+describe('QA notify template branch trigger (regression guard)', () => {
+  // -Contribution repos are ALSO a mixture of `main`- and `master`-default
+  // branches (Tutorials-Contribution defaults to `master`). The QA template
+  // MUST scope the push trigger to the default branch(es) — WITHOUT a branches:
+  // filter it fires on EVERY branch push (e.g. the devtoberfest validation-
+  // tutorial bot's `validation-tutorial/*` branches), dispatching a QA rebuild
+  // for a slug that exists only on that branch; QA discovery reads the default
+  // branch, so the slug is a phantom and the rebuild hard-fails "unknown slug
+  // in filter" (tutorials-ims#2097). Keep this in parity with the PROD guard.
+  const template = readFileSync(
+    join(__dirname, '..', '..', '.github', 'workflows', 'notify-qa.yml.template'),
+    'utf8',
+  )
+
+  it('fires on both master and main', () => {
+    expect(template).toMatch(/branches:\s*\[\s*master\s*,\s*main\s*\]/)
+  })
+
+  it('does not ship a main-only trigger', () => {
+    expect(template).not.toMatch(/branches:\s*\[\s*main\s*\]/)
+  })
+
+  it('ships a branches filter (never an unfiltered push trigger)', () => {
+    expect(template).toMatch(/branches:/)
+  })
+})