Allow pushing to the task-assigned branch, not just claude/* branches

Feature Request

Problem

When Claude Code deskopt/web (not CLI) is invoked with a task that specifies a target branch (e.g., via a GitHub issue or PR review workflow), the git proxy restricts pushes to only claude/* branches. This means Claude cannot push directly to the branch it was asked to work on.

In practice, this forces an awkward workaround:

1. Claude creates a claude/* side branch
2. Pushes fixes there
3. Creates a separate PR to merge the side branch into the actual target branch
4. The user has to merge that PR manually

The end result is the same commits landing on the same branch, but with extra friction, noise (extra PRs, extra branches to clean up), and confusion for the user.

Proposed Solution

Allow the git proxy to also permit pushes to the branch specified in the task instructions. The proxy already knows which branch Claude is supposed to work on — it's in the task configuration. Allowing pushes to that specific branch (in addition to claude/* branches) would eliminate the roundabout workflow while maintaining safety.

This would not weaken the safety model — Claude still couldn't push to main, other feature branches, or any branch not explicitly assigned. It would just remove an unnecessary restriction on the one branch Claude was told to use.

Current Behavior

• Claude is assigned to work on branch 127-auto-chat-titling (a PR feature branch)
• Claude can fetch/checkout that branch
• Claude cannot push to it (403 from proxy)
• Claude can push to claude/pr-129-review-fixes-KKnEk
• User must manually merge or Claude must create a secondary PR

Expected Behavior

• Claude is assigned to work on branch 127-auto-chat-titling
• Claude can push directly to 127-auto-chat-titling
• No extra branches or PRs needed