fix(ci): resolve version-bump checkout failure when GH_TOKEN secret is absent

[Copilot]

The version-bump workflow fails immediately at actions/checkout@v4 because secrets.GH_TOKEN is not configured — GitHub evaluates the missing secret as "", which the action rejects as "Input required and not supplied: token".

Change

Use || github.token as a fallback in the checkout token input:

# .github/workflows/version-bump.yml
token: ${{ secrets.GH_TOKEN || github.token }}

When GH_TOKEN (PAT for branch-protection bypass) is present it takes precedence; otherwise the job falls back to the built-in GITHUB_TOKEN, which already has contents: write via the job's permissions block.

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