docs: Fix postis.js description in CLAUDE.md

Changed from 'Legacy postMessage utility' to 'Third-party postMessage utility'
since postis.js is actively used by PostMessageTransportBackend, not legacy code.

Author: hristoterezov

CLAUDE.md

@@ -47,19 +47,12 @@ The codebase is organized as a collection of independent utility modules, each i
   - Handles MESSAGE_TYPE_EVENT, MESSAGE_TYPE_REQUEST, MESSAGE_TYPE_RESPONSE
   - Implements pluggable backends via `setBackend()`
   - `PostMessageTransportBackend.js` - postMessage-based backend
-  - `postis.js` - Legacy postMessage utility
+  - `postis.js` - Third-party postMessage utility (used by PostMessageTransportBackend)
 
 - **uri/** - URI manipulation utilities
 
 ### Entry Point
 The main `index.js` re-exports all module functionality:
-```javascript
-export * from './avatar/index.js';
-export * from './browser-detection/index.js';
-export * from './jitsi-local-storage/index.js';
-export * from './json.ts';
-export * from './polyfills/index.ts';
-```
 
 ### TypeScript Configuration
 - Target: ES6 modules
@@ -97,4 +90,3 @@ The project is gradually migrating from JavaScript to TypeScript. When adding fe
 ## Testing and CI
 - CI runs on pull requests via GitHub Actions
 - Linting is enforced in CI (no test suite currently defined)
-- Uses Node 16 in CI environment