wiring sees no sender for bump-ready, so the umbrella's v0.15.0 bump is red #161

The umbrella's v0.15.0 bump PR marola-dev/marola#862 is red: wiring --check (run 38995875072, quality-other)
says dispatch `bump-ready` is listened for but never sent. wiring.py finds a dispatch's type in
event_type=…, in an EVENT* env next to /dispatches, or in an events array; notify-devkit.yml (#158) puts
it in a JSON literal (-d '{"event_type":"bump-ready",…}'), so no repo is ever a sender. Every orphan dispatch fails
--check, in both directions, and wiring.allow covers artifacts only. The umbrella cannot take v0.15.0, and a
consumer's bump-ready.yml caller (marola-dev/marola#859's sub-issues) would make the umbrella's pointer-sync PR red
the other way ("sent but never listened for") while the umbrella still pins v0.14.0.

Acceptance criteria

• notify-devkit.yml names its type in the dispatch step's env (EVENT_TYPE: bump-ready) and builds the body from
  it, so wiring.py sees every caller as a bump-ready sender.
• notify-devkit-test.yml calls marola-dev/marola-devkit/.github/workflows/notify-devkit.yml@vX.Y.Z (the tagged
  path, which release.py moves), not ./, so the devkit itself is a sender and the umbrella's bump is green
  before any consumer has a caller.
• Released as v0.15.1. The seven callers pin v0.15.1, and the code repos' callers merge only after the umbrella's
  main pins v0.15.1.

Named test

• wiring.py --devkit <this branch, tagged v0.15.1 locally> on the umbrella lists
  | `bump-ready` | marola-devkit `notify-devkit-test.yml` (`notify-devkit.yml@v0.15.1`, by hand) | marola-devkit `bump-merge.yml` |
  (today the sender column is —); devkit-quality rc=0.
• Live: the umbrella's v0.15.1 bump PR has quality-other green.