## Summary
- Visual regression dispatch was failing for external contributor PRs
because fork PRs don't have access to repo secrets
(`CI_PRIVILEGED_DISPATCH_TOKEN`)
- Moved the dispatch from inline jobs in `ci-front.yaml` / `ci-ui.yaml`
to a new `workflow_run`-triggered workflow
- `workflow_run` runs in the base repo context and always has access to
secrets, regardless of whether the PR is from a fork
- Follows the same pattern already used by `post-ci-comments.yaml` for
breaking changes dispatch
- Handles the fork case where `workflow_run.pull_requests` is empty by
falling back to a head label search
## Test plan
- [ ] Verify CI Front and CI UI workflows still pass without the removed
jobs
- [ ] Verify the new `visual-regression-dispatch.yaml` triggers after CI
Front / CI UI complete
- [ ] Test with a fork PR to confirm the dispatch succeeds
