Implemented automatic addition of "// Last modified: [timestamp]" headers across command and internal files for better tracking. Updated prompts in agent and edit commands to enforce header format. Added logic to prepend header if missing in generated content. Fixed minor issues like missing newlines at end of files.
Introduce new `agent` command that scans .go files in the project, generates an AI-driven plan for changes based on user instruction, and applies edits with previews and backups. Includes integration with Grok client for planning and content generation.
Update existing files with timestamp comments as part of the agent's editing demonstration. Add agentCmd to root command.
