fix(ci): backport beta channel readback retry to main

[wgqqqqq]

Summary

Backport #2827 to main. Desktop Package run 34043857456 published all five platform packages for v1.0.0-beta.2, then failed because the immediate Beta channel readback did not match the uploaded version. The fix previously landed only on 1.0.0-explore; main still checked the response content once.

Retry stale manifest content, transport errors, and malformed responses with a bounded wait, while failing if the expected version never appears. Keep the existing Beta promotion and stable channel policy.

Type and Areas

Bug fix / CI — Desktop release publication.

Verification

• pnpm run check:github-config: 22 passed, 1 skipped because PowerShell is unavailable locally.
• Regression executes the workflow shell against stale content followed by success, transient transport failure, malformed JSON, and persistent stale content.
• git diff --check: passed.
• Current v1.0.0-beta.2 release and channel-beta manifests match; stable latest remains v0.2.19.

Reviewer Notes

No runtime behavior changed; remote scenarios are not affected or exercised. This PR only backports publication verification and does not enable additional Beta artifact types.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.