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/state/snapshot.rs

@@ -0,0 +1,22 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct StateSnapshot {
+    pub snapshot: serde_json::Value,
+}
+
+impl StateSnapshot {
+    pub fn new() -> Self {
+        StateSnapshot {
+            snapshot: serde_json::json!({}),
+        }
+    }
+}
+
+pub fn serialize_snapshot(snapshot: &StateSnapshot) -> anyhow::Result<Vec<u8>> {
+    Ok(serde_json::to_vec(snapshot)?)
+}
+
+pub fn deserialize_snapshot(data: &[u8]) -> anyhow::Result<StateSnapshot> {
+    Ok(serde_json::from_slice(data)?)
+}