fix(cli): rename syncs local config + picker shows display name

After renaming the mesh display name on the server, the launch
picker still showed the slug ("flexicar-2") because (a) local
config.json was not updated and (b) the picker only printed
mesh.slug. Now: rename writes the new name back into config.json
on success, and the picker prints "name (slug)" when they differ.
Also surfaces a hint that slugs are immutable (today).

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

apps/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "claudemesh-cli",
-  "version": "1.19.2",
+  "version": "1.19.3",
   "description": "Peer mesh for Claude Code sessions — CLI + MCP server.",
   "keywords": [
     "claude-code",