fix(ci): remove unnecessary rebase step causing dirty tree error in release workflow

[Copilot]

The release workflow was failing with a "dirty tree" error during the rebase step. The error occurred because:

1. The bump_version.py script modifies pubspec.yaml and CHANGELOG.md
2. The workflow commits these changes to prepare the release
3. The workflow then attempts to rebase onto origin/main, which conflicts with the committed changes

Run git fetch origin main
From https://github.com/pckimlong/riverboot
 * branch            main       -> FETCH_HEAD
error: cannot rebase: You have unstaged changes.
error: Please commit or stash them.
Error: Process completed with exit code 1.

Root Cause: The rebase step was unnecessary since the release workflow only runs on pushes to the main branch. There's no need to rebase when we're already working on the target branch.

Solution: Removed the "Rebase onto latest main" step from .github/workflows/release.yml. The workflow now follows a cleaner, more logical flow:

1. Run version bump script
2. Commit the changes
3. Create release tag
4. Push changes and tag
5. Create GitHub release

This eliminates the source of the conflict while maintaining all the release functionality.

Fixes #13.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://storage.googleapis.com/flutter_infra_release/flutter/c29809135135e262a912cf583b2c90deb9ded610/dart-sdk-linux-x64.zip
  • Triggering command: curl --retry 3 --continue-at - --location --output /tmp/flutter/bin/cache/dart-sdk-linux-x64.zip REDACTED (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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[Copilot]

Pull Request Overview

This PR fixes a CI workflow issue where the release workflow was failing due to a "dirty tree" error caused by an unnecessary rebase step. The workflow was attempting to rebase after committing version bump changes, which created conflicts since the workflow already runs on the main branch.

• Removed the problematic "Rebase onto latest main" step from the release workflow
• Simplified the release flow to avoid git conflicts while maintaining all functionality