Refactor API integration and enhance command handling

- Removed unused modules and updated module paths for clarity.
- Added autocomplete functionality for command input in InputState.
- Updated AppStateRest to include a method for checking if a turn is in flight.
- Refactored subagent engine to use new API client structure.
- Changed default provider from "openrouter" to "zen" with updated API keys and models.
- Implemented tests for memory management and edit log functionalities.
- Enhanced error handling in API requests and improved response parsing.
- Updated UI components to reflect new API provider and status indicators.

src/view/mod.rs

@@ -201,7 +201,7 @@ fn render_overlay(frame: &mut Frame, area: Rect, overlay: crate::app::state::typ
                     Style::default().fg(Theme::DIM),
                 )),
                 Line::from(Span::styled(
-                    "  OpenRouter  - Multi-model API gateway",
+                    "  Zen API      - opencode.ai free model",
                     Style::default().fg(Theme::TEXT),
                 )),
                 Line::from(Span::styled(