TEMPORARY: proving workflow_dispatch checks satisfy branch protection (do not merge)

[cubehouse]

Throwaway experiment, will be closed and the branch deleted. Do not merge.

Establishing whether a workflow_dispatch run's check runs satisfy required status checks on a PR, before rewiring the drift job on this basis.

push and pull_request are removed from ci.yml on this branch only, so opening this PR reproduces the bot PR's situation exactly: zero check runs, blocked on reports it cannot receive. CI is then dispatched against the branch, and the question is whether the resulting checks land on this PR's head SHA and clear protection.

[cubehouse]

Experiment complete, closing. Result recorded on the tracking issue.

Two runs on this same PR, same required contexts, differing only in trigger event:

event	sha	run	PR
workflow_dispatch	8921fb59	success, 3 check runs with the exact required names on the SHA	BLOCKED, rollup showed 0 checks
push	a03bf181	success	CLEAN

So a dispatched run does not satisfy branch protection even when its check runs sit on the PR head SHA under the right names and its check suite reports as linked to the PR. A push-event run does.