feat(agent): wire git_tools into AI tool registry with full schemas
- ChatService: add tools() method to expose registered tool definitions
- RoomService: populate AiRequest.tools from chat_service.tools(), enable tools
with max_tool_depth=3 (was always None)
- ToolHandler: add pub new() constructor so git_tools modules can register
handlers with full schema metadata
- Add description + JSON schema params to all 16 git tools:
git_log, git_show, git_search_commits, git_commit_info, git_graph,
git_reflog, git_branch_list, git_branch_info, git_branches_merged,
git_branch_diff, git_diff, git_diff_stats, git_blame, git_file_content,
git_tree_ls, git_file_history, git_tag_list, git_tag_info
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