ci: revert allowing hotfix/* in authorize

[daniel-graham-amplitude]

Reverts #1717

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Note

Medium Risk
Changes release workflow gating and removes hotfix/* support in the initial authorization step, which could block intended release runs from hotfix branches. Impact is limited to CI/CD behavior but affects the publishing path.

Overview
Tightens publish-v2.yml authorization branch protection by removing hotfix/* support and requiring the workflow to be triggered from main (except for dry-run, which still allows any branch).

Also simplifies the branch-check step by inlining GitHub context variables instead of passing them via step env.

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