Add graph viewport controls

docs/CONTRACT.md

@@ -23,7 +23,7 @@ approved contract and measured cross-project evidence; it is not an unimplemente
 - Result envelope: `schemas/result.schema.json`, version 1.
 - Changeset schema: `schemas/changeset.schema.json`, version 1.
 - Index schema: version 1, disposable and reproducible.
-- Core, CLI, and MCP server: version 0.7.0.
+- Core, CLI, and MCP server: version 0.7.1.
 
 Schema files describe the generic interchange contract. Runtime validation remains responsible for
 path confinement, source hashing, relationship resolution, dependency cycles, project limits, stale
@@ -105,6 +105,11 @@ overview, bounded search, exact node content, and bounded incoming-and-outgoing
 There is no write endpoint, arbitrary query endpoint, static filesystem handler, external asset,
 or project-selection control.
 
+The `graph-browser@2` template provides mouse-wheel zoom centered on the pointer, left-button drag
+pan, explicit zoom-in and zoom-out buttons, a reset-view button, and a live zoom percentage. A
+four-pixel drag threshold preserves node activation for ordinary clicks. Loading another root node
+resets the viewport so the new neighborhood begins centered and fully framed.
+
 One MCP process owns at most one listener. Repeated invocations reuse it and may replace its
 validated snapshot only after a fresh index check. The listener stops with the MCP process.
 Project-specific integrations receive the same tool because it operates on the supplied