ci: remove broken changeset-bot workflow

[byungsker]

Overview

Remove .github/workflows/changeset-bot.yml, which has been failing on every PR since it was merged in #350 (2026-03-31).

Root Cause

The workflow references changesets/bot@v1:

jobs:
  bot:
    runs-on: ubuntu-latest
    steps:
      - uses: changesets/bot@v1

But changesets/bot is a GitHub App (https://github.com/apps/changeset-bot), not a GitHub Action:

• The repository has no action.yml / action.yaml at the root.
• It has no releases and no tags, so @v1 cannot resolve.

As a result, every PR fails with:

##[error]Unable to resolve action `changesets/bot@v1`, unable to find version `v1`

See https://github.com/toss/react-simplikit/actions/runs/24677120915/job/72164079866 for a recent example.

Why Remove Instead of Fix

The intended functionality (PR comments about changeset status) is provided by the Changeset Bot GitHub App, not a workflow. The correct setup is:

1. Install the app at https://github.com/apps/changeset-bot (repo admin action).
2. No workflow is needed — the app automatically comments on PRs.

Keeping a broken workflow alongside the app would only add a noisy failing check.

Impact

• Unblocks CI on all open PRs (e.g. fix: alias mobile source in vite example to avoid prebuild requirement #370).
• Release workflow (release.yml) is unaffected — it uses changesets/action@v1, which is the correct, existing action.

Checklist

• Did you write the test code?
  • N/A — CI workflow cleanup
• Have you run yarn run fix to format and lint the code and docs?
  • N/A — no source files changed
• Have you run yarn run test:coverage to make sure there is no uncovered line?
  • N/A — no source files changed
• Did you write the JSDoc?
  • N/A — no public API change