chore: bump version to 1.2.0 and sync all plugin manifests

- Sync .claude-plugin/plugin.json (was stuck at 1.1.0) and .cursor-plugin/plugin.json (was 1.0.5) to match main version
- Update CLAUDE.md versioning section to list all four files that must be kept in sync
- Document scripts/generate-large-graph.mjs in CLAUDE.md

.cursor-plugin/plugin.json

@@ -2,7 +2,7 @@
   "name": "understand-anything",
   "displayName": "Understand Anything",
   "description": "AI-powered codebase understanding — analyze, visualize, and explain any project",
-  "version": "1.0.5",
+  "version": "1.2.0",
   "author": {
     "name": "Lum1104"
   },