feat: add draggable graph zones

docs/graph-explorer-contract.md

@@ -173,6 +173,11 @@ When access-zone grouping is selected, boundaries use `accessZone` values such
 as `private-dev`, `collaborator-test`, `production-public`, or
 `production-admin`.
 
+Zone labels should be rendered as plain text in the upper-left corner of the
+zone rectangle, without badge frames or white backgrounds. The label may still
+act as the zone's focus/drag handle as long as it visually reads as text drawn
+on the zone surface.
+
 Useful warnings for the graph explorer include:
 
 - control surfaces in user-facing access zones;
@@ -202,6 +207,11 @@ are summarized on the zone node rather than rendered. Expanding the zone removes
 the synthetic elements and restores the original graph elements without
 changing the underlying payload.
 
+Zone dragging is also view-only. Dragging a zone handle should translate the
+currently assigned visible member nodes by the same delta and then recompute the
+overlay bounds from the new node positions. The operation updates Cytoscape view
+coordinates only; it does not change Fabric graph data.
+
 ## Repo-Scoping Compatibility
 
 Repo-scoping can adapt without a rewrite because its current graph payload