Update headless command execution to use the new architecture:
- Removed CommandResult import (no longer needed)
- Headless mode now creates an App instance and uses cmd_context()
- Commands are parsed and executed via the registry, effects applied
through app.apply_effects() instead of command::dispatch()
- Made cmd_context() public so headless mode can access it
- Updated persistence save to use app.model instead of direct model
Tests updated to use ExecuteCommand instead of QuitCmd, with proper
buffer setup for command parsing.
Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/Qwen3.5-35B-A3B-GGUF:Q5_K_M)
32716ebc16