Add graph viewport controls

SLICE_HISTORY.md

@@ -1,5 +1,36 @@
 # Completed slices
 
+## DFG-11 graph viewport navigation
+
+### Changed
+
+- Released the fixed `graph-browser@2` template with pointer-centered mouse-wheel zoom.
+- Added left-button drag pan with pointer capture and a four-pixel movement threshold.
+- Preserved normal node activation by suppressing click navigation only after an actual drag.
+- Added keyboard-operable zoom-in, zoom-out, and reset buttons plus a live zoom percentage.
+- Reset the viewport whenever a new root neighborhood loads.
+- Kept all viewport behavior client-side without adding HTTP endpoints or project authority.
+- Released the compatible change as DocForge 0.7.1.
+
+### Verification
+
+- Focused HTTP tests and embedded JavaScript syntax validation cover button zoom, reset,
+  pointer-centered wheel zoom, left-drag pan, and preserved node-click handling. The current agent
+  runtime did not expose its rendered browser automation connection, so no rendered interaction
+  claim is made for this gate.
+- The complete warning-strict DocForge suite passes.
+
+### Limits
+
+- Viewport position is session-local and is not persisted.
+- The radial layout itself remains deterministic and fixed.
+- A minimap, saved node positions, and alternate layouts remain outside the current contract.
+
+### Next gate
+
+No further gate is planned. Measure dense-graph use before adding more navigation or layout
+features.
+
 ## DFG-10 project-bound graph visualization
 
 ### Changed