fix(release): allow explore beta packaging

[wgqqqqq]

Summary

Allow Desktop Beta releases to build commits from the protected 1.0.0-explore history while preserving the existing Stable restriction to protected main history.

Type and Areas

Type: CI / release regression fix

Areas: Desktop packaging, release safety

Motivation / Impact

The current release workflow rejects every 1.0.0-explore commit because it only accepts commits reachable from main. This blocks the requested v1.0.0-beta.1 release.

Stable releases remain restricted to main. Beta releases may additionally use commits reachable from the protected 1.0.0-explore branch. Arbitrary refs remain rejected.

Verification

• pnpm run check:github-config — 20 passed, 1 platform-dependent test skipped
• git diff --check

Reviewer Notes

The release will remain frozen to pre-change explore SHA 66709c3c7a4bb1455447af8783e2ef5a17d24152; this workflow-only fix will not enter the Beta product artifact.

Checklist

• This PR is focused and contains no unrelated artifacts.
• Relevant verification is recorded above.
• No user-facing strings or locales are affected.

[wgqqqqq]

Pausing the upstream release path; validating and publishing v1.0.0-beta.1 in the fork first.