chore: bump version to 2.4.0

PR #108 ships a new user-visible feature (in-dashboard source code viewer
with Files tab + double-click navigation), so it warrants a minor bump
across all 5 version-tracked files.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.copilot-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "understand-anything",
   "description": "AI-powered codebase understanding — analyze, visualize, and explain any project",
-  "version": "2.3.2",
+  "version": "2.4.0",
   "author": {
     "name": "Lum1104"
   },