Two-node DB-consumer bed + a scenario disk field

The GREEN multi-node regression bed that proves the DB-consumer gate: substrate/control on
one node, postgres+redis providers and baserow+letta consumers on another, each consumer
getting its own credential and its own mesh-named database across the overlay. Requires the
mesh-control provider-seal-key fix and the mesh-catalog db-name fix.

Includes a general lab capability: a machine 'disk' field sizing the VM root disk (a broad
install exhausts the pool default and the host fails mid-apply with 'no space left on
device'). The bed sets 60GiB.

Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF

src/declaration/types.ts

@@ -110,6 +110,13 @@ export interface Machine {
    */
   memory?: string;
   cpus?: number;
+  /**
+   * Root disk size, e.g. "60GiB". Left unset, the VM uses the storage pool's default, which is
+   * enough for a handful of modules. A broad install that stocks many runtime + service images
+   * (each hundreds of MB, the heavy app images over a GB) exhausts the default and the host fails
+   * mid-apply with "no space left on device" — a disk fact about the machine, not a mesh defect.
+   */
+  disk?: string;
 }
 
 /** Reachability between segments, as a segmented router enforces it. Asymmetric by design. */