5.2 Snapshot lifecycle

# 5.2 Snapshot lifecycle

**Parent:** Story 5 (#7232)
**Tool file:** `forge/ee/lib/mcp/tools/snapshots.js` (extend)

## Summary

Complete snapshot management. List and create already ship; this adds the read surface (get/full) and the write lifecycle (export, import, edit, set-target) plus deletes. Snapshots span both hosted instances and devices, plus a generic `/snapshots/:id` surface. Deletes are separated from ordinary writes so MCP clients gate them behind confirmation by default.

Start in forge/ee/lib/mcp/tools/snapshots.js and read the existing list and create implementations. Map the requested get/full, export, import, edit, set-target, and delete surfaces across hosted instances, devices, and /snapshots/:id. Done means the read and write lifecycle is covered, with deletes separated for confirmation gating.

Written by the indexing model from the issue text.