Task 6: Migrate RLM to use native tools=[] and simplify review flow

- Updated _ensure_configured() to pass tools=self._create_tool_functions() to dspy.RLM()
- Simplified review() and review_local() to use direct rlm.aforward() calls
- Removed AGENTIC_TOOLS_PROMPT constant (~60 lines)
- Removed _process_tool_requests() and _run_rlm_with_tools() methods (~140 lines)
- Removed unused state dicts (_repo_files, _repo_dirs, _search_results)
- Removed unused imports (re, Prediction, REPLHistory)
- Updated class docstring to reference native DSPy RLM tools
- Kept _load_local_checklist(), review_pr(), review_issue() aliases
- Implemented on_step callback using result.trajectory if available

Agent-Id: agent-367d7d70-1d10-4e5d-9d84-ec8956d914ae

Author: sng-asyncfunc