fix(graph): stop corpus-graph labels overlapping

Labels piled on top of each other (esp. in the neighborhood view) for two
reasons, both fixed in graph-canvas.tsx:

1. Font grew as you zoomed OUT (size was divided by sqrt(globalScale) and had
   a +6 floor), so at overview zoom labels became huge and collided. Now the
   label font is a ~constant SCREEN size (fontPx / globalScale).

2. Every node drew its label at once. Now labels are zoom-gated: at overview
   zoom only the active node, the 3 practice-area hubs, and the most-cited
   precedents (size>=4) are labeled; topic hubs appear at >=1.05 and the rest
   at >=1.5 — by which point there is pixel room between nodes.

Also: a white halo (strokeText) behind each label for legibility over edges
and nearby nodes, and stronger d3 forces (charge -220, link distance 60) so
nodes spread out and labels have more room.

web-ui build passes; /graph in the route table.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web-ui/src/components/graph/graph-canvas.tsx

@@ -130,6 +130,17 @@ export function GraphCanvas({
     fgRef.current?.zoomToFit?.(400, 60);
   }, []);
 
+  // Spread nodes out so labels have room — stronger repulsion + longer links
+  // than the d3-force defaults (charge -30, link 30). Re-applied whenever the
+  // graph data changes (full ↔ neighborhood).
+  useEffect(() => {
+    const fg = fgRef.current;
+    if (!fg?.d3Force) return;
+    fg.d3Force("charge")?.strength?.(-220);
+    fg.d3Force("link")?.distance?.(60);
+    fg.d3ReheatSimulation?.();
+  }, [graphData]);
+
   const drawNode = useCallback(
     (node: FGNode, ctx: CanvasRenderingContext2D, globalScale: number) => {
       const r = nodeRadius(node);
@@ -147,22 +158,39 @@ export function GraphCanvas({
         ctx.stroke();
       }
 
-      // Labels: hubs always; precedents when zoomed in, important, or active.
+      // Labels — gated by zoom so they don't pile up. At overview zoom only a
-      const isHub = node.type === "topic" || node.type === "practice_area";
+      // few show (active node, the 3 practice-area hubs, the most-cited
+      // precedents); zooming in reveals the rest, by which point there is pixel
+      // room between nodes. Font is kept at a ~constant SCREEN size (px /
+      // globalScale) instead of growing as you zoom out — that growth was what
+      // made labels collide.
+      const isTopicHub = node.type === "topic";
+      const isAreaHub = node.type === "practice_area";
       const showLabel =
         !dimmed &&
-        (isHub || node.id === activeId || node.size >= 3 || globalScale >= 1.6);
+        (node.id === activeId ||
+          isAreaHub ||
+          globalScale >= 1.5 ||
+          (isTopicHub && globalScale >= 1.05) ||
+          (!isTopicHub && node.size >= 4 && globalScale >= 0.9));
       if (showLabel && node.label) {
-        const fontSize = Math.max(2.5, (isHub ? 4.5 : 3.6) / Math.sqrt(globalScale)) +
+        const fontPx = isTopicHub || isAreaHub ? 12 : 11;
-          (isHub ? 1 : 0);
+        const fontSize = fontPx / globalScale; // ~constant on screen
-        ctx.font = `${fontSize + 6}px Heebo, sans-serif`;
+        ctx.font = `${fontSize}px Heebo, sans-serif`;
         ctx.textAlign = "center";
         ctx.textBaseline = "top";
         ctx.direction = "rtl";
-        ctx.fillStyle = isHub ? "#7a5a26" : "#1a1a2e";
         const label =
-          node.label.length > 28 ? `${node.label.slice(0, 27)}…` : node.label;
+          node.label.length > 22 ? `${node.label.slice(0, 21)}…` : node.label;
-        ctx.fillText(label, node.x ?? 0, (node.y ?? 0) + r + 1);
+        const lx = node.x ?? 0;
+        const ly = (node.y ?? 0) + r + 2 / globalScale;
+        // White halo so the text stays readable over edges and nearby nodes.
+        ctx.lineWidth = 3 / globalScale;
+        ctx.strokeStyle = "rgba(255,255,255,0.92)";
+        ctx.lineJoin = "round";
+        ctx.strokeText(label, lx, ly);
+        ctx.fillStyle = isTopicHub || isAreaHub ? "#7a5a26" : "#1a1a2e";
+        ctx.fillText(label, lx, ly);
       }
       ctx.globalAlpha = 1;
     },