feat: add UI settings and translations for assistantMessageParser experiment

- Add English translations for the experimental feature
- Add translations for all supported languages (ca, de, es, fr, hi, id, it, ja, ko, nl, pl, pt-BR, ru, tr, vi, zh-CN, zh-TW)
- The experiment now appears in the UI settings under Experimental features
- Description explains the performance benefits of the new parser

Author: daniel-lxs

webview-ui/src/i18n/locales/ca/settings.json

@@ -679,9 +679,13 @@
 			"name": "Enable concurrent file edits",
 			"description": "When enabled, Roo can edit multiple files in a single request. When disabled, Roo must edit files one at a time. Disabling this can help when working with less capable models or when you want more control over file modifications."
 		},
-		"PREVENT_FOCUS_DISRUPTION": {
+"PREVENT_FOCUS_DISRUPTION": {
 			"name": "Background editing",
 			"description": "Prevent editor focus disruption when enabled. File edits happen in the background without opening diff views or stealing focus. You can continue working uninterrupted while Roo makes changes. Files can be opened without focus to capture diagnostics or kept closed entirely."
+		},
+		"ASSISTANT_MESSAGE_PARSER": {
+			"name": "Use new message parser",
+			"description": "Enable the experimental streaming message parser that provides significant performance improvements for long assistant responses by processing messages more efficiently."
 		}
 	},
 	"promptCaching": {