fix(client): treat HTTP 202 Accepted as valid session termination (#3546)

[teddiesloco]

Summary

Addresses #3546 by recognizing HTTP 202 (Accepted) alongside 200 and 204 as valid success status codes when terminating a streamable-HTTP session via DELETE.

Per RFC 9110 §9.3.5, a server may respond with 202 Accepted to a DELETE request if the deletion action is queued or scheduled asynchronously (common in reverse proxies, serverless gateways, and async session teardown). Previously, the client logged a WARNING: Session termination failed: 202 despite the request succeeding.

Closes #3546.

[github-actions]

This PR has been closed automatically. This repo only keeps pull requests open when they come from a maintainer, or from a contributor a maintainer has assigned to the linked issue, and you aren't currently assigned to #3546.

If a maintainer assigns you to #3546, this PR reopens on its own and there's nothing more you need to do here. Assignment is a maintainer call based on capacity; comments that only ask to be assigned don't factor in. What does help is engaging on the issue itself by confirming the repro, explaining why it matters for your use case, or describing the approach you'd take.

You're welcome to keep pushing commits here (just avoid force-pushing, since GitHub can't reopen a rewritten branch), but that on its own won't get the PR reviewed or the issue assigned, and realistically most auto-closed PRs stay closed. There's no need to open a new PR either way.

CONTRIBUTING.md has the full reasoning, but in short:

• We're a small team with very little capacity to review community PRs right now.
• Many recent PRs are AI-generated with little human review, and reviewing one carefully still costs a maintainer as much time as it ever did. A well-described issue is usually more useful to us than the code.

Maintainers: reopen, remove missing-issue-link, or add bypass-issue-check to override.