ci(lint): run os-regen-merge's --self-test, mirroring the verify-lock step

.github/workflows/lint.yml

@@ -1037,6 +1037,40 @@ jobs:
  - name: PM ci-failure self-test
  run: node scripts/pm/ci-failure.mjs --self-test
 
+ # os-regen-merge self-test (#12893). Mirrors the `Verify-lock entry-point
+ # self-test` step above 1:1 — same directory, same split between the tool
+ # and its self-test. `scripts/pm/os-regen-merge.sh` is the mechanized merge
+ # sequence for a branch touching os-regen-driven generated artifacts, and it
+ # has NO CI path at all: it is run BY HAND inside a feature branch's
+ # worktree, on a merge that exists only there. Its header says so, and that
+ # is deliberate.
+ #
+ # The SELF-TEST is a different animal from the script it tests. It needs no
+ # worktree, no remote and no merge — only `git` and a temp dir — and it
+ # builds five small fixture repos to pin 23 cases: the PER-FILE merge-side
+ # selection and its per-path notices, the staged-diff sentence, the
+ # uncommitted-hand-off refusal, and the four pre-existing refusals. A few
+ # seconds, no network.
+ #
+ # Left unwired it rots the way this repo has already recorded and fixed
+ # twice (#11514, #6008): the next refactor of the script reds nothing. Two
+ # of the 23 cases are SOURCE SCANS of the script's own text — they assert
+ # step 2 keeps the non-staging `git restore --source` spelling and never the
+ # staging `git checkout` one — which is to say they are precisely the rows a
+ # future edit invalidates silently and precisely the rows no reviewer reads.
+ # Nothing but this step is an instrument for them.
+ #
+ # Unconditional and un-`if:`-ed, like every self-test around it — an
+ # exemption is precisely what a self-test must not have, or the gap simply
+ # moves. One `--self-test` per `run:` block, deliberately: the masking shape
+ # `check-step-collectors.mjs` guards is a block driving TWO OR MORE distinct
+ # scripts. A discovery collector over `scripts/pm/*.sh --self-test` — which
+ # would also catch the next such script arriving unwired — is ruled out of
+ # this card: two literal steps do not yet justify the machinery, and a third
+ # is when to revisit it.
+ - name: os-regen-merge self-test
+ run: bash scripts/pm/os-regen-merge.sh --self-test
+
  # Claude hook guard self-tests (#11514, objectstack half of
  # objectstack-ai/objectui#5754). `.claude/hooks/` holds the enforcement
  # behind the two rules whose violation is most expensive in this repo —