Refactor edit and scaffold commands to support invocation from chat --agent mode by using temporary global variables for passing instructions/descriptions. Add interactive prompts for normal usage, preview diffs, and confirmation before writing files. Update chat handler to set these variables and reset after execution.
- Replace WriteString + Sprintf with Fprintf in harvestContext for better performance.
- Wrap deferred Chdir in scaffold tests with error logging to avoid silent failures.
Introduce a new `scaffold` command that uses Grok to generate new files based on a description.
Includes options for generating tests, dry runs, force overwrite, and language override.
Detects language from file extension and harvests project context for better generation.
