Add TUI rendering for CustomMessageEntry

- Add CustomMessageComponent with purple-tinted styling
- Add theme colors: customMessageBg, customMessageText, customMessageLabel
- Rename renderMessages to renderSessionContext taking SessionContext directly
- renderInitialMessages now gets context from sessionManager
- Skip rendering for display: false entries

packages/coding-agent/src/main.ts

@@ -77,7 +77,7 @@ async function runInteractiveMode(
 		}
 	});
 
-	mode.renderInitialMessages(session.state);
+	mode.renderInitialMessages();
 
 	if (migratedProviders.length > 0) {
 		mode.showWarning(`Migrated credentials to auth.json: ${migratedProviders.join(", ")}`);