chore(scripts): delete the four root scripts held back from the first cleanup PR (#26266)

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Part of #26091 — the second half of Wanted 1. The first half landed as
#26235, split there to stay under the 3,000 changed-line human-merge
threshold. Wanted 2 (one invocation spelling) is still on the card, so
#26091 remains open.

Clause-②: no
Metadata-protocol: none

## What changed

Deletes the four root scripts that #26235 held back. The census method
and positive control are the same as in that PR: the file stem is
grepped over the whole tree, with `scripts/check-nul-bytes.mjs` as the
control. The census was re-run on `main` at `81bba6c3f`.

| Script | What still names it |
|---|---|
| `scripts/measure-markdown-ts-blocks.mjs` | shipped `CHANGELOG.md`
entries only (release-owned, left as shipped) |
| `scripts/measure-reserved-identity-name-census.mjs` | one shipped
`CHANGELOG.md` entry only |
| `scripts/pm/measurement-claim-triage.mjs` | one historical census row
in a `scripts/pm/dispatch-gates.mjs` docblock; the prose beside it now
says the tool is held at commit `7111e14ac9` |
| `scripts/bench/runtime-publish-gate.bench.mts` | the path string
`scripts/pm/dispatch-gates.self-test.mjs` (fast tier, lines 4441 and
4470) hands to `isInRootTsProgram` / `changeKindLines`: pure string
predicates that read no disk, so the fixture still means "a new
TypeScript script in the root tree" |

The branch took `origin/main` by merge rather than a reset, because its
name is not `claude/issue-*` and AGENTS.md §3 then treats it as shared
(no force-push). The diff against `main` is these five files only.

## Acceptance

- Census re-run on the head: none of the four has a caller left. What
remains is the two `CHANGELOG.md` mentions, the docblock row (now
commit-pinned) and the fixture string.
- Derived gate families (`dispatch-gates --commands`): 33 derived at
`77e4b93c5`. All 33 were run and every one exited 0, including
`check:pm-dispatch-gates` (fast tier: 1917 cases pass). `dispatch-gates
--ran` reports "33 run, 0 NOT-MEASURED".
- `check:pm-dispatch-gates`, both tiers: `node
scripts/pm/check-dispatch-gates.mjs --slow` at `77e4b93c5`:
"dispatch-gates self-test: 2182 cases pass", exit 0.
- `check:type-check-debt` (the root tsc program loses one `.mts` file):
exit 0. The root tsc program still has 26 errors and none is above its
record, so the deleted file carried none.

## Acceptance notes

- Changed lines: +2 / −2,942 = 2,944, under the 3,000 threshold.

---
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---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: objectstack-fleet[bot]