Add create-branch.yml GitHub Actions workflow

[Copilot]

This PR adds a new GitHub Actions workflow that allows users to create and push new branches to the repository through the GitHub Actions interface.

Features

The new create-branch.yml workflow provides:

• Manual trigger: Uses workflow_dispatch to allow on-demand execution
• User input: Requires a mandatory name string parameter for the branch name
• Proper permissions: Has contents: write permission to create and push branches
• Error handling: Checks for existing branches and fails gracefully if a branch already exists
• User feedback: Provides a workflow summary with branch details and a direct link to the new branch

Implementation Details

The workflow follows GitHub Actions best practices:

• Uses actions/checkout@v5 with full git history (fetch-depth: 0)
• Configures git with the standard GitHub Actions bot identity
• Validates branch names don't already exist remotely before creation
• Uses proper shell scripting practices (passes actionlint validation)
• Provides clear error messages and success feedback

Usage

Users can trigger this workflow from the Actions tab by:

1. Selecting "Create Branch" workflow
2. Clicking "Run workflow"
3. Entering the desired branch name
4. The workflow will create and push the new branch

This addresses the need for a simple, user-friendly way to create branches without requiring local git operations or direct repository access.

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:

• api.contoso.com
  • Triggering command: /tmp/go-build3396865111/b278/cli.test -test.testlogfile=/tmp/go-build3396865111/b278/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true (dns block)
  • Triggering command: /tmp/go-build1409158599/b278/cli.test -test.testlogfile=/tmp/go-build1409158599/b278/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true (dns 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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