fix: use main branch for changesets/bot action

[guesung]

Summary

• Fix changesets/bot@v1 action resolution failure — the changesets/bot repo has no v1 tag/release
• Change to changesets/bot@main so the workflow can resolve the action

Test plan

• Verify the Changeset Bot workflow passes on new PRs

[Copilot]

Pull request overview

Updates the Changeset Bot GitHub Actions workflow to resolve an action reference that cannot be fetched as changesets/bot@v1 by switching to the repository’s default branch.

Changes:

• Update workflow action reference from changesets/bot@v1 to changesets/bot@main.

[Copilot]

Using a floating ref (changesets/bot@main) makes this workflow non-deterministic and increases supply-chain risk, especially with pull_request_target and pull-requests: write permissions (the action code can change without review). Prefer pinning the action to an immutable commit SHA (or a trusted, signed tag/release if one becomes available) and update it intentionally when needed.

Suggested change

	- uses: changesets/bot@main
	- uses: changesets/bot@3b4cf1f2c9a6c1891d3dbed1d5d295df1b548d64 # pinned from @main

[kimyouknow]

@guesung Thanks for fixing the bot failure from #350!

All our other actions are SHA-pinned for supply-chain security
(see #325). Could you pin this one too?

[guesung]

@kimyouknow Thanks for the review! I've pinned it to a full commit SHA in bcf5104.

I pinned to e755cedfffdc49f54ce5daa69d960a143941b787(current master HEAD).