Implement chat and markdown views, enhance status bar, and add workflow panel

- Added `chat.rs` for rendering chat messages with timestamps and roles.
- Introduced `markdown.rs` for rendering markdown content with styling.
- Created `status.rs` to display the application status bar with session and message counts.
- Developed `workflow.rs` to show the current workflow status, including tool calls and active jobs.
- Established a `theme.rs` for centralized color management across the UI.
- Updated `mod.rs` to include new modules and manage rendering logic.

src/app/mod.rs

@@ -0,0 +1,11 @@
+pub mod catastrophic;
+pub mod harness;
+pub mod mode;
+pub mod runtime;
+pub mod state;
+pub mod workflow;
+pub mod subagent;
+pub mod review;
+pub mod bgbash;
+pub mod mcp;
+pub mod sec;