Remove plan for splitting large JavaScript files

Removed the plan to split large JavaScript files into smaller modules due to prioritization changes.

docs/ROADMAP.md

@@ -30,15 +30,6 @@
 
 *Prioritized for upcoming phases.*
 
-### 1. Split large JavaScript files into smaller modules
-
-- **Priority:** P1
-- **Category:** Maintainability / AI Context Optimization
-- **Background:** Core files like `background.js` and `popup.js` have grown large and exceed 800 lines. This makes manual debugging harder and wastes context window space for AI models.
-- **Planned solution:**
-  - Structurally split logic into separate focused modules (e.g., UI Renderer, Message Router, Storage Manager, Socket Client).
-  - Use ES modules for clean separation and better reusability.
-
 ### 2. Invite link with target URL for auto-redirect
 
 - **Priority:** P2