feat(tui): introduce comprehensive state management for TUI interface

- Add AppStateRest as the central state struct for managing TUI state.
- Implement InputState for handling user input, autocomplete, and history.
- Create MiscState to manage overlays, notifications, and editor state.
- Introduce ScrollState for viewport scrolling functionality.
- Develop TranscriptCache for efficient message rendering in the chat pane.
- Implement SimpleAgent and SimpleWorkflowEngine for agent lifecycle management.
- Add helper functions for managing effort levels and token counting.
- Organize state-related modules for better maintainability and clarity.

apps/domain/src/lib.rs

@@ -53,6 +53,11 @@ pub use core::{
     ToolCallResult, ToolDef, ToolFunction, ToolFunctionDef, UsageStats,
 };
 pub use error::DomainError;
+
+// Agent module top-level items (TurnEvent, SessionRuntime, etc.)
 pub use agent::*;
+// Sub-module items need explicit re-exports
+pub use agent::progress::AgentProgress;
+pub use agent::prompt::{compaction_prompt, main_agent_prompt, subagent_directive};
 pub use workflow::*;
 pub use subagent::*;