fix(cli): session config.json written 0600, not 0644 (1.35.1)

The per-session config written to the launch tmpdir embeds the mesh
keypair (secret key) but was created without a mode → 0644
(world/group-readable), which `claudemesh status` flags as
"perms 0644 — expected 0600". The enclosing mkdtemp dir is 0700, but
lock the file down too so the secret is never world-readable. File is
freshly created in a new tmpdir, so the mode applies on create.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "claudemesh-cli",
-  "version": "1.35.0",
+  "version": "1.35.1",
   "description": "Peer mesh for Claude Code sessions — CLI + MCP server.",
   "keywords": [
     "claude-code",