Add setting to hide/disable the 'Create PR' button in the git status bar

Feature Request

Summary

Add a configurable setting to hide or disable the Create PR button that appears in the git status bar when Claude Code detects a branch diverged from another.

Current Behavior

When on a branch with commits ahead of another (e.g., master ← claudio), a persistent Create PR button appears in the status bar UI. There is no setting to hide or remove it.

promptSuggestionEnabled: false does not affect this button — it only controls suggestion chips in the input area.

Desired Behavior

A setting such as showCreatePrButton: false (or extending promptSuggestionEnabled to cover this button) that allows users to hide the Create PR button from the status bar.

Use Case

Some users manage PRs externally (via CLI, GitHub UI, etc.) and find the persistent button unnecessary UI noise. Others may have workflows where the button is not applicable.

Proposed Setting

// ~/.claude/settings.json
{
  "showCreatePrButton": false
}