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/tool/git_cred.rs

@@ -0,0 +1,50 @@
+use serde_json::{json, Value};
+use anyhow::{Result, anyhow};
+use std::process::Command;
+use super::Tool;
+use super::ToolCtx;
+
+pub struct GitCred;
+
+impl Tool for GitCred {
+    fn name(&self) -> &'static str {
+        "git_cred"
+    }
+
+    fn description(&self) -> &'static str {
+        "Interact with git credential helper (store, get, erase credentials)"
+    }
+
+    fn parameters(&self) -> Value {
+        json!({
+            "type": "object",
+            "properties": {
+                "operation": {
+                    "type": "string",
+                    "enum": ["store", "get", "erase"],
+                    "description": "Git credential operation"
+                }
+            },
+            "required": ["operation"]
+        })
+    }
+
+    fn run(&self, _ctx: &ToolCtx, args: &Value) -> Result<String> {
+        let operation = args.get("operation")
+            .and_then(|v| v.as_str())
+            .ok_or_else(|| anyhow!("missing required argument: operation"))?;
+        let output = Command::new("git")
+            .arg("credential")
+            .arg(operation)
+            .output()
+            .map_err(|e| anyhow!("git credential failed: {}", e))?;
+        if output.status.success() {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_string();
+            let stderr = String::from_utf8_lossy(&output.stderr).to_string();
+            Ok(format!("{}{}", stdout, stderr))
+        } else {
+            let stderr = String::from_utf8_lossy(&output.stderr).to_string();
+            anyhow::bail!("git credential '{}' failed: {}", operation, stderr.trim())
+        }
+    }
+}