test(release): the dry-run safety probe matched a prompt that no longer exists (#3045)

## A release-safety alarm that was firing on wording

```
AssertionError: dry-run must exit before proceed confirmation
```

The probe searched for ``await confirm(`Proceed with release``. The
prompt has since become:

```js
await confirm(`Proceed with ${CHANNEL} release v${chosenVersion} (build, publish to npm tag '${NPM_DIST_TAG}', tag)?`)
```

so `indexOf` returned **-1**, `dryRunExitIndex < -1` was false, and this
has been red on `main` ever since.

## The property itself holds — verified directly, not inferred from a
green suite

| | offset |
| --- | --- |
| first `if (DRY_RUN) {` guard, calling `process.exit(0)` | **28808** |
| the sole `await confirm(` call site | **44503** |

Two dry-run exit guards, one confirmation, exit first. **`pnpm release
--dry-run` cannot reach the proceed prompt.** This was never a real
safety failure.

The probe is narrowed to the stable prefix `await confirm(\`Proceed with
`, which still names the one confirmation in the file while surviving
the interpolated channel and version. The sentence was never the safety
property.

## Why this one mattered more than an ordinary stale probe

A stale probe on a *safety* test spends the alarm on cosmetics. Everyone
learns the assertion is red for no reason — so a genuine reordering
later arrives at an alarm nobody reads. That is a worse outcome than the
test not existing.

## Proven to still catch the real regression

I injected a `confirm(` call **above** the first dry-run exit in
`release.mjs`:

```
confirm injected before the dry-run exit  →  ℹ pass 5   ℹ fail 1   (dry-run must exit before proceed confirmation)
reverted                                  →  ℹ pass 6   ℹ fail 0
```

**No release command was run.** The mutation was local to a scratch copy
of `release.mjs`, reverted immediately, and the working tree verified
clean — `release.mjs` is untouched by this commit, and the diff is the
test file only.

## Fifth and last of the mechanically-fixable suites

That closes the mechanical half of the seven red `scripts/__tests__`
suites I found: `plugin-authoring-docs` (#3036), `verify-fast` (#3038),
`ci-test-shard-timings` (#3040), `engine-vitest-gate-policy` (#3044),
and this.

**`workflow-reliability-release-check` is the one that is not
mechanical** and I am still not touching it: its acceptance map cites 13
test files with **8 missing** and **2 of 5 rows carrying zero surviving
evidence**. That needs its owner to decide, per row, whether the
coverage moved or was deleted — a repoint would launder the gap
(diagnosed on #3036).

Five of six looked identical from the failure line. Only that one is
unsafe to fix without owning the subject.

## Verification (measured)

- this suite — **6 passed / 0 failed** (was 1 failed)
- `eslint` — clean

Test-only. No changeset.

scripts/__tests__/release-prompt-gate.test.mjs

@@ -63,7 +63,23 @@ test("release script dry-run exits before proceed confirmation and gates ask thr
   const promptGateIndex = source.indexOf("shouldPromptForVersion({ dryRun: DRY_RUN, autoYes: AUTO_YES, interactive: INTERACTIVE })");
   const askIndex = source.indexOf("await ask(`Release version");
   const dryRunExitIndex = source.indexOf("if (DRY_RUN) {");
-  const confirmIndex = source.indexOf("await confirm(`Proceed with release");
+  /*
+  FNXC:ReleaseSafety 2026-07-31-21:40:
+  Probe the STABLE prefix, not the whole sentence — the interpolated part is not the safety property.
+
+  This read `await confirm(\`Proceed with release`, and the prompt has since become
+  `Proceed with ${CHANNEL} release v${chosenVersion} (...)`. `indexOf` returned -1, the comparison
+  `dryRunExitIndex < -1` was false, and this assertion has been red on `main` ever since — reporting a
+  release-safety failure that did not exist.
+
+  The property itself still holds and was verified directly rather than inferred from the green:
+  the first `if (DRY_RUN) {` guard sits at 28808 and calls `process.exit(0)`; the sole `await confirm(`
+  call site is at 44503. Two dry-run exit guards, one confirmation, and the exit precedes it.
+
+  A stale probe on a SAFETY test is worse than on an ordinary one: it spends the alarm on wording, so
+  a genuine reordering later arrives at an assertion everyone has learned is red for cosmetic reasons.
+  */
+  const confirmIndex = source.indexOf("await confirm(`Proceed with ");
 
   assert.notEqual(promptGateIndex, -1, "release.mjs should use the pure prompt gate");
   assert.notEqual(askIndex, -1, "release.mjs should still support version prompts");