Avoid running the stateless Vitest probe twice in CI and release

At reviewed SHA `811d6a267b34f1eba2ed0969dd24ccdda565371b`, both CI and release run `test/stateless.test.ts` once through `check:stateless` and again through the unfiltered full test suite.

- Keep the unique static lint in `check:stateless`.
- Remove one of the two behavioral invocations; the current duplicate also launches two fresh Node subprocesses each time.
- Preserve one explicit behavioral probe so the statelessness contract remains merge-blocking.

Verification and scope

Exact reviewed locations:

- dedicated Vitest invocation: [`scripts/check-stateless.mjs:67-72`](https://github.com/Comfy-Org/comfy-multi-player/blob/811d6a267b34f1eba2ed0969dd24ccdda565371b/scripts/check-stateless.mjs#L67-L72)
- subprocess work inside the test: [`test/stateless.test.ts:47-56`](https://github.com/Comfy-Org/comfy-multi-player/blob/811d6a267b34f1eba2ed0969dd24ccdda565371b/test/stateless.test.ts#L47-L56)
- CI runs `check:stateless` and later unfiltered `npm test`: [`.github/workflows/ci.yml:44-72`](https://github.com/Comfy-Org/comfy-multi-player/blob/811d6a267b34f1eba2ed0969dd24ccdda565371b/.github/workflows/ci.yml#L44-L72)
- release repeats the same sequence: [`.github/workflows/release.yml:49-65`](https://github.com/Comfy-Org/comfy-multi-player/blob/811d6a267b34f1eba2ed0969dd24ccdda565371b/.github/workflows/release.yml#L49-L65)
- `npm test` is unfiltered `vitest run`: [`package.json:32`](https://github.com/Comfy-Org/comfy-multi-player/blob/811d6a267b34f1eba2ed0969dd24ccdda565371b/package.json#L32)

Independent verification reproduced the workflow semantics from source. It could not produce a meaningful timing measurement in the fresh clone because dependencies were not installed; the duplicate invocation itself is deterministic from the scripts.

Open heads #123, #138, #142, and #143 do not modify these paths. Existing #149/#150 and merged #140 are unrelated.

Reviewed SHA: `811d6a267b34f1eba2ed0969dd24ccdda565371b`.

Compare scripts/check-stateless.mjs:67-72 with the test steps in .github/workflows/ci.yml:44-72 and .github/workflows/release.yml:49-65; package.json:32 shows that npm test runs unfiltered vitest. Remove the duplicate behavioral invocation while retaining the static lint and one explicit stateless probe, then verify the affected workflows and test configuration still run the intended checks once.

Written by the indexing model from the issue text.