feat: Add tool permissions for creating commits and pushing branches

[CharlotteS34]

Feature Request

Description

Add two new granular tool permissions to the MCP server to allow consumers to scope
access for Git write operations independently:

• repo_create_commit — Permission to create commits in a repository
• repo_push_branch — Permission to push a branch to a remote

Motivation

The current permission model does not expose commit and push operations as separate
controllable permissions. These are distinct Git operations and should be grantable
independently — for example, an agent may be permitted to stage and create commits
for human review without having permission to push those commits upstream.

This follows the principle of least privilege and is consistent with existing
fine-grained permissions such as repo_create_branch and repo_create_pull_request.

Relevant REST Endpoints

• Create a commit (push): POST https://dev.azure.com/{organization}/{project}/_apis/git/repositories/{repositoryId}/pushes?api-version=7.1
  • Reference: https://learn.microsoft.com/en-us/rest/api/azure/devops/git/pushes/create

Acceptance Criteria

• A new repo_create_commit tool permission is added
• A new repo_push_branch tool permission is added
• Both permissions are documented in TOOLSET.md