fix: publish one combined GitHub release

[ArekChr]

Summary

Changesets currently creates a GitHub release for every published package. Create one combined release on the existing main package tag instead, with notes collected from all packages in the fixed release group.

• Disable per-package GitHub releases while keeping package tags and npm publishing managed by Changesets.
• Combine changelog entries for the exact release version, list all released packages, and omit empty note sections. Include fixtures from 5.4.2.
• Preserve an existing GitHub release and support retrying release creation after all package tags have reached GitHub.
• Run the release automation tests in CI and document the release and retry behavior.

Validation

• node --test .github/scripts/*.test.mjs — 18 tests passed, including 5.4.2 notes, one release for six packages, existing releases, and retry behavior.
• Biome 2.5.6 check for .github/scripts and package.json — passed.
• actionlint 1.7.7 for both changed workflows — passed.
• git diff --check — passed.
• Package build, typecheck, and full monorepo tests were not run locally.

Scope

This covers the current fixed group containing @callstack/repack. Missing or mismatched package tags require manual verification and repair before retrying; the script does not recover npm publications or recreate tags. Canary publishing is unchanged.

[vercel]

@ArekChr is attempting to deploy a commit to the Callstack Team on Vercel.

A member of the Team first needs to authorize it.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 42c734b

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

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