feat: collapse mesh.name and mesh.slug into one identifier (v1.21.0)

Pre-launch fix: every visible surface already keyed on slug, so
"name" was a parallel string that only existed to confuse users
on rename ("I renamed but nothing visible changed").

Now slug IS the identifier. claudemesh rename <old> <new> is the
whole rename surface. PATCH /api/cli/meshes/:slug body becomes
{ slug } and the route writes both columns to keep them in sync.
Mesh create derives slug from input.name and stores name = slug.
Pickers drop the (parens). The claudemesh slug verb shipped 30
min ago is removed — merged into rename.

The mesh.name DB column stays for now to avoid touching ~25
reader sites; a follow-up migration drops it.

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

apps/cli/src/ui/welcome/MeshPickerStep.ts

@@ -1,10 +1,10 @@
 import type { JoinedMesh } from "~/services/config/facade.js";
-import { bold, dim } from "../styles.js";
+import { bold } from "../styles.js";
 
 export function renderMeshPicker(meshes: JoinedMesh[]): void {
   console.log("\n  Select a mesh:\n");
   meshes.forEach((m, i) => {
-    console.log("    " + bold((i + 1) + ")") + " " + m.slug + " " + dim("(" + m.name + ")"));
+    console.log("    " + bold((i + 1) + ")") + " " + m.slug);
   });
   console.log("");
 }