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

docs/MCP_CONTRACT.md

@@ -61,7 +61,7 @@ only through the explicit local CLI integration command.
 
 ## Visualization boundary
 
-`docforge_visualize` starts the fixed built-in `graph-browser@1` template against the currently
+`docforge_visualize` starts the fixed built-in `graph-browser@2` template against the currently
 validated derived index. It may focus one stable node, run one bounded lexical query, or open the
 project overview. The tool returns a loopback URL and exact snapshot identity.
 
@@ -69,6 +69,8 @@ The tool cannot select a project, database, template, host, port, filesystem pat
 expression. Its HTTP surface is token-bound, read-only, same-origin, and limited to overview,
 search/filter, and node-neighborhood JSON. The browser exposes an exact validated index snapshot.
 It rejects index replacement or alteration and requires another MCP invocation to refresh.
+Viewport interaction is entirely client-side: wheel zoom, left-button drag pan, explicit zoom
+buttons, and reset never request or mutate project data.
 
 ## Excluded tools