- New edit_file(path, old_string, new_string, replace_all) function
- Reads/writes with newline='' to preserve CRLF and 1-space indentation
- Returns error if old_string not found or multiple matches without replace_all
- Added to MUTATING_TOOLS for HITL approval routing
- Added to TOOL_NAMES and dispatch function
- Added MCP_TOOL_SPECS entry for AI tool declaration
- Updated agent configs (tier2, tier3, general) with edit_file mapping
Note: tier1, tier4, explore agents don't need this (edit: deny - read-only)
