Fix markdown streaming duplication by splitting newlines first

- Added string-width library for proper terminal column width calculation
- Fixed wrapLine() to split by newlines before wrapping (like Text component)
- Fixed Loader interval leak by stopping before container removal
- Changed loader message from 'Loading...' to 'Working...'

packages/tui/package.json

@@ -40,7 +40,8 @@
 		"@types/mime-types": "^2.1.4",
 		"chalk": "^5.5.0",
 		"marked": "^15.0.12",
-		"mime-types": "^3.0.1"
+		"mime-types": "^3.0.1",
+		"string-width": "^8.1.0"
 	},
 	"devDependencies": {
 		"@xterm/headless": "^5.5.0",