feat: add manually dispatchable workflow to switch changeset pre mode

[fabiankaegy]

What

Adds a way to switch the changeset pre-release mode directly from the GitHub Actions UI, without needing a local checkout.

• New Changeset Mode workflow (workflow_dispatch): pick the target branch in the dispatch dropdown and choose a mode:

  • exit-pre (promote to actual release) — runs npx changeset pre exit, commits .changeset/pre.json, and pushes
  • enter-pre (next) — the reverse, puts the branch back into next pre-release mode

  Both directions no-op with a message if the branch is already in the requested state, mirroring the guards in the existing release workflow.

• Release workflow now supports workflow_dispatch: the mode-switch commit is pushed with the default GITHUB_TOKEN, which intentionally does not trigger other workflows — so after switching modes you can kick a release run manually on the same branch (or just wait for the next regular push).

Notes

• Exiting pre mode on develop is not immediately undone by the auto "Enter pre next" step: changeset pre exit leaves pre.json in place (marked exited), so the [[ ! -f pre.json ]] guard stays false until changeset version removes the file. Once the release lands, the next develop push re-enters next mode as before.
• The new workflow becomes dispatchable in the Actions UI once this lands on the default branch.

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[changeset-bot]

⚠️ No Changeset found

Latest commit: 05a416a

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.

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