feat(mcp): enhance MCP server registration with error handling and improve transport process management

refactor: update various tools for better error handling and path resolution
fix: improve markdown rendering and input display in TUI

apps/infrastructure/src/mcp/manager.rs

@@ -32,7 +32,13 @@ impl Default for McpManager {
 
 impl McpManager {
 
-    pub fn register(&mut self, name: &str, transport: &str) {
+    /// Register an MCP server by name and transport string.
+    ///
+    /// Returns an error if a server with the same name is already registered.
+    pub fn register(&mut self, name: &str, transport: &str) -> anyhow::Result<()> {
+        if self.servers.contains_key(name) {
+            anyhow::bail!("MCP server '{name}' is already registered");
+        }
         self.servers.insert(
             name.to_string(),
             McpServerHandle {
@@ -40,10 +46,12 @@ impl McpManager {
                 transport: transport.to_string(),
             },
         );
+        Ok(())
     }
 
-    pub fn unregister(&mut self, name: &str) {
-        self.servers.remove(name);
+    /// Remove a registered MCP server and return its handle, if it existed.
+    pub fn unregister(&mut self, name: &str) -> Option<McpServerHandle> {
+        self.servers.remove(name)
     }
 
     pub fn list(&self) -> Vec<McpServerHandle> {