Refactor git tools: replace 4 tools with 11 focused implementations

[will-lamerton]

Summary

Replaced the existing 4 git tools with 11 focused, well-designed tools that cover core git operations needed by a coding agent. A viable closing of #98 - I know this PR pulls away from that, but testing this PR makes git operations intelligent, automatic and easy to understand.

Changes

Deleted Tools:

• git_smart_commit - Over-engineered, models can write commit messages directly
• git_create_pr - Only generated templates, replaced with actual PR creation
• git_branch_suggest - Unnecessary, models can suggest branch names
• git_status_enhanced - Replaced with simpler git_status

New Tools (11):

• git_status - Show repository status, branch, sync state
• git_diff - Show unstaged, staged, or branch diffs
• git_log - View commit history with filters
• git_add - Stage files for commit
• git_commit - Create commits
• git_push - Push to remote
• git_pull - Pull from remote with rebase option
• git_branch - List, create, switch, or delete branches
• git_stash - Save, list, apply, pop, or clear stashes
• git_reset - Unstage files or reset commits
• git_pr - Create, view, or list GitHub PRs (via gh CLI)

Improvements

• Consistent error handling across all git tools
• Improved user feedback messages
• Standardized parameter handling
• Removed redundant code
• Fixed typos and improved command descriptions
• Better tool approval levels (AUTO, STANDARD, ALWAYS_APPROVE)
• Added comprehensive test coverage

Testing

Updated git-tools.spec.tsx to individual test files for all tools improving coverage.

Bonus: If git is not installed, tools won't be registered, saving ~2,000-4,000 tokens.