fix(ci): don't clobber a fork PR's green "E2E Tests" on a label event

Same defect as the e2e-report fix, on the fork path. main's `labeled`
pull_request trigger produces a "Pull Request" run whose `plan` guard
discards every label but full-e2e, so every job skips and nothing is built.
workflow_run still fires for it, and `resolve` then reddened the required
status down either branch: a non-success conclusion fails closed, and a
`success` conclusion falls through to the missing-pr-patch check, which also
fails closed. Labelling an already-green open fork PR therefore turned its
E2E Tests red until the next push.

Detect that shape directly — the triggering run's `Plan build` job concluded
`skipped` — and return without posting anything. Statuses are per-SHA and an
unposted required status stays "Expected", which blocks the merge, so
declining to post can only preserve a verdict some real run reached, never
invent one. A fork that edits the workflow to force this path leaves its head
SHA with no status at all, i.e. not mergeable. The job already holds the
actions:read scope the job lookup needs.

Signed-off-by: Myasnikov Daniil <myasnikovdaniil2001@gmail.com>

.github/workflows/e2e-fork.yaml

@@ -108,6 +108,27 @@ jobs:
               core.setOutput('should_run', 'false');
             };
 
+            // Discarded label event: pull-requests.yaml triggers on `labeled` but
+            // its `plan` guard discards every label other than full-e2e, so such a
+            // run skips every job and builds nothing. Post NOTHING and stop —
+            // deciding here would overwrite an already-green status with red (via
+            // the CONCLUSION check or the missing-pr-patch check below) every time
+            // anyone labels an open fork PR. Fail-closed: statuses are per-SHA and
+            // an unposted required status stays "Expected", which blocks the merge,
+            // so declining to post can only ever preserve a verdict a real run
+            // reached — never invent one. A fork editing the workflow to force this
+            // path just leaves its head SHA with no status, i.e. not mergeable.
+            const jobs = await github.paginate(
+              github.rest.actions.listJobsForWorkflowRun,
+              { owner, repo, run_id: RUN_ID, per_page: 100 },
+            );
+            const plan = jobs.find(j => j.name === 'Plan build');
+            if (plan && plan.conclusion === 'skipped') {
+              console.log(`Triggering run ${RUN_ID} skipped 'Plan build' (discarded label event) — leaving "E2E Tests" untouched.`);
+              core.setOutput('should_run', 'false');
+              return;
+            }
+
             // Fork build did not succeed → fail the required status (fail-closed).
             if (CONCLUSION !== 'success') {
               await decide('failure', `Pull Request workflow concluded '${CONCLUSION}'; e2e not run`);