Pond graph: size the canvas to the viewport, not the width ratio (#131)

The SVG scaled to container width with height following the fixed
800×560 viewBox ratio — on wide windows the graph grew taller than the
viewport, the page got a scrollbar, and wheel-zoom scrolled along.
The graph page is now a flex column filling the main column; the canvas
takes the remaining height (flex: 1, min-height: 0), a ResizeObserver
feeds its measured size to ForceGraph as width/height, and the SVG
fills it exactly. LocalGraphPanel keeps its fixed defaults. Scope
deliberately layout-only (issue comment 1187): with no scrollbar there
is nothing for the wheel to scroll, so no non-passive listener needed.
The graph pack now asserts the main column does not overflow
vertically on the graph route.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Fb2VzvcoBPHkjh8bZ6PzQn

apps/web/e2e/graph.spec.ts

@@ -72,6 +72,15 @@ test('pond graph renders the link structure and creates phantom pages', async ({
   expect(await page.locator('.force-graph__edge').count()).toBeGreaterThanOrEqual(2);
   await expect(page.locator('.graph-legend')).toBeVisible();
 
+  // #131: the page fits the viewport — wheel-zoom must never scroll along,
+  // so the main column may not grow a vertical scrollbar on this route.
+  expect(
+    await page.evaluate(() => {
+      const main = document.querySelector('.main')!;
+      return main.scrollHeight - main.clientHeight;
+    }),
+  ).toBeLessThanOrEqual(0);
+
   // #123: the physics/rendering sliders are there and take effect — the
   // font-size slider writes straight into the SVG labels.
   const controls = page.locator('.graph-controls');

apps/web/src/graph/PondGraphPage.tsx

@@ -1,7 +1,7 @@
 import type { PageView, PondGraphView, PondView } from '@dorfteich/shared';
 import { DEFAULT_LABEL_COLOR } from '@dorfteich/shared';
 import { useQuery, useQueryClient } from '@tanstack/react-query';
-import { useMemo } from 'react';
+import { useEffect, useMemo, useRef, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { useNavigate, useParams } from 'react-router-dom';
 
@@ -125,11 +125,37 @@ function GraphView({
     graphSettingsKey(pondId),
     GRAPH_SETTINGS_DEFAULTS,
   );
+  // #131: the canvas flexes to the remaining viewport height; its measured
+  // size becomes the SVG viewBox, so the graph fills it exactly instead of
+  // deriving its height from the width (which used to overflow the page).
+  const canvasRef = useRef<HTMLDivElement>(null);
+  const [size, setSize] = useState<{ width: number; height: number } | null>(null);
+  useEffect(() => {
+    const canvas = canvasRef.current;
+    if (!canvas) return;
+    const observer = new ResizeObserver((entries) => {
+      const rect = entries[0]?.contentRect;
+      if (rect && rect.width > 0 && rect.height > 0) {
+        setSize({ width: Math.round(rect.width), height: Math.round(rect.height) });
+      }
+    });
+    observer.observe(canvas);
+    return () => observer.disconnect();
+  }, []);
   return (
     <>
       <GraphControls settings={settings} setSettings={setSettings} />
-      <div className="graph-page__canvas">
-        <ForceGraph nodes={nodes} edges={edges} settings={settings} onNodeClick={onNodeClick} />
+      <div className="graph-page__canvas" ref={canvasRef}>
+        {size !== null && (
+          <ForceGraph
+            nodes={nodes}
+            edges={edges}
+            width={size.width}
+            height={size.height}
+            settings={settings}
+            onNodeClick={onNodeClick}
+          />
+        )}
       </div>
     </>
   );

apps/web/src/styles/base.css

@@ -1776,6 +1776,16 @@ button {
 }
 
 /* Knowledge graph (issue #112) + local graph panel (#113). */
+
+/* #131: the page fills the main column as a flex column, so the canvas can
+   take exactly the remaining viewport height — the page itself must never
+   grow a scrollbar (wheel-zoom would scroll along with it). */
+.graph-page {
+  height: 100%;
+  display: flex;
+  flex-direction: column;
+}
+
 .graph-page__header {
   display: flex;
   align-items: baseline;
@@ -1799,6 +1809,14 @@ button {
   border-radius: var(--radius);
   background: var(--color-surface);
   overflow: hidden;
+  flex: 1;
+  min-height: 0;
+}
+
+/* The pond graph SVG gets its measured container size as viewBox (#131), so
+   it may fill the canvas exactly; the local panel keeps width-scaled sizing. */
+.graph-page__canvas .force-graph {
+  height: 100%;
 }
 
 /* Physics/rendering sliders (#123). */