ci: rename branch-protection caller job id to branch-protection

[rubenvdlinde]

GitHub names a reusable-workflow status context <caller-job-id> / <called-job-name>.

This branch's caller job id was not branch-protection, so the shared branch-protection
workflow reported under the wrong context name, and the org ruleset requirement
branch-protection / check-branch never reported at all — not as a failure, as nothing.

Several of these beta branches carry a second, independent fault: the reusable workflow was
referenced as Conduction/.github instead of ConductionNL/.github. The Conduction org does not
exist (GET /repos/Conduction/.github -> 404), so on those branches the workflow could not even
resolve. Where present, that is fixed here too — renaming the job id alone would not have made the
context appear.

This matters for beta -> main promotion PRs, whose head is beta, so beta's tip is what
decides the context name and the workflow reference.

Does not change what is required and does not touch any ruleset or branch protection.

[rubenvdlinde]

Still needed, and it fixes more than the title says. Left open — beta is
human-gated.

beta's copy of this workflow is wrong in two ways, not one:

$ git show origin/beta:.github/workflows/branch-protection.yml
  jobs:
    check:                                                  <- 1. wrong job id
      uses: Conduction/.github/.github/workflows/branch-protection.yml@main
             ^^^^^^^^^^                                     <- 2. wrong ORG

The org is Conduction, not ConductionNL. Every other workflow on every other
branch of this repo says ConductionNL. This PR corrects both — the diff changes
the uses: line as well as the job id — so the title undersells it and a reviewer
skimming for "just a rename" would miss half of it.

The job-id half matters for the same reason as #43: GitHub names a
reusable-workflow context <caller-job-id> / <called-job-name>, so check:
produces check / check-branch while the org ruleset requires
branch-protection / check-branch, and the required check never reports. On this
PR's own head the fixed context resolves and passes —
branch-protection / check-branch SUCCESS, alongside Branch Policy Check SUCCESS. Those are the only two checks that run here at all.

Blocker: base is beta. beta is human-gated, so this is not mine to merge
regardless of how green it is. Needs a human.

Sequencing note: #43 is the identical job-id fix for main (whose uses: line is
already correct — only beta carries the org typo). They are independent; neither
blocks the other.