fix(release): isolate flaky SDK publication probes

[antonvishal]

Why

A pre-existing release test flake is blocking the Grok Build PR, #2876. Its 20 ms deadline probe shares an HTTP server and request counter with a later 503 assertion, so a late aborted request can inflate that assertion. Failing CI run.

What

Give 404-then-200 publication, immediate 503 rejection, and persistent-404 deadline expiry independent tests and servers. Assert the SDK request paths, exactly one 503 request, and an actual 404 retry before expiry. Advance only Date.now for the deadline case, keeping real HTTP requests and network timers. The existing stalled-request test remains; production code is unchanged.

How

Validated 154 root unit tests, 20 runs of the four HTTP scenarios totaling 80 test executions, tooling typecheck, formatting, and lint.

---

Summary by cubic

Fixes a flaky release test by giving each SDK publication probe its own HTTP server and request counter, so a late aborted request from one scenario no longer inflates the 503 assertion's request count in scoped-release.test.ts.

• Splits the shared 404-then-200 publication, immediate-503 rejection, and deadline-expiry scenarios into separate tests.
• Asserts exact request paths, exactly one 503 request, and an actual 404 retry before expiry.
• Mocks only Date.now for the deadline case, keeping real HTTP requests and network timers.
• Leaves production code unchanged.

^{Written for commit ed36d23. Summary will update on new commits.}

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