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/model/conversation.rs

@@ -0,0 +1,46 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Conversation {
+    pub messages: Vec<crate::dto::chat::message::ChatMessage>,
+    pub system_prompt: String,
+    pub session_id: String,
+    pub model: String,
+    pub max_tokens: u32,
+    pub temperature: f32,
+}
+
+impl Conversation {
+    pub fn new(system_prompt: String, session_id: String) -> Self {
+        Conversation {
+            messages: Vec::new(),
+            system_prompt,
+            session_id,
+            model: "anthropic/claude-opus-4-8".to_string(),
+            max_tokens: 8192,
+            temperature: 0.7,
+        }
+    }
+
+    pub fn push(&mut self, msg: crate::dto::chat::message::ChatMessage) {
+        self.messages.push(msg);
+    }
+
+    pub fn rebuild_system(&mut self, new_prompt: String) {
+        self.system_prompt = new_prompt;
+        self.messages.retain(|m| {
+            !matches!(m.role, crate::dto::chat::message::Role::System)
+        });
+    }
+
+    pub fn to_api_messages(&self) -> Vec<crate::dto::chat::message::ChatMessage> {
+        let mut msgs = Vec::with_capacity(self.messages.len() + 1);
+        msgs.push(crate::dto::chat::message::ChatMessage::system(&self.system_prompt));
+        msgs.extend(self.messages.iter().cloned());
+        msgs
+    }
+
+    pub fn len(&self) -> usize {
+        self.messages.len()
+    }
+}