feat(scene): shared zoom/pan for control and presentation

Keep effects pinned to map coordinates when the viewport changes; materials/NPC overlays stay screen-fixed.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/main/sceneView/sceneViewStore.test.ts

@@ -0,0 +1,67 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+
+import {
+  DEFAULT_SCENE_VIEW_CAMERA,
+  sceneViewPanBy,
+  sceneViewZoomAt,
+} from '../../shared/types/sceneView';
+
+import { SceneViewStore } from './sceneViewStore';
+
+describe('SceneViewStore', () => {
+  it('resets to default camera', () => {
+    const store = new SceneViewStore();
+    store.dispatch({ kind: 'set', camera: { scale: 2, ox: 0.2, oy: 0.8 } });
+    const next = store.dispatch({ kind: 'reset' });
+    assert.equal(next.scale, 1);
+    assert.equal(next.ox, 0.5);
+    assert.equal(next.oy, 0.5);
+  });
+
+  it('clamps scale and origin', () => {
+    const store = new SceneViewStore();
+    const next = store.dispatch({ kind: 'set', camera: { scale: 99, ox: -1, oy: 2 } });
+    assert.equal(next.scale, 8);
+    assert.equal(next.ox, 0);
+    assert.equal(next.oy, 1);
+  });
+});
+
+describe('sceneViewZoomAt / panBy', () => {
+  it('zooms toward cursor and keeps that content point under cursor', () => {
+    const hostW = 1000;
+    const hostH = 500;
+    const containW = 800;
+    const containH = 400;
+    const hostX = 700;
+    const hostY = 250;
+    const next = sceneViewZoomAt(DEFAULT_SCENE_VIEW_CAMERA, {
+      hostW,
+      hostH,
+      containW,
+      containH,
+      hostX,
+      hostY,
+      factor: 2,
+    });
+    assert.ok(next.scale > 1.5);
+    const displayW = containW * next.scale;
+    const displayH = containH * next.scale;
+    const left = hostW / 2 - next.ox * displayW;
+    const top = hostH / 2 - next.oy * displayH;
+    const ix = (hostX - left) / displayW;
+    const iy = (hostY - top) / displayH;
+    // At scale=1 contain is centered; cursor was at content x=(700-100)/800=0.75
+    assert.ok(Math.abs(ix - 0.75) < 1e-6);
+    assert.ok(Math.abs(iy - 0.5) < 1e-6);
+  });
+
+  it('pans in host pixels', () => {
+    const cam = { scale: 2, ox: 0.5, oy: 0.5 };
+    const next = sceneViewPanBy(cam, { containW: 400, containH: 200, dx: 80, dy: 0 });
+    // displayW=800; dx=80 → ox decreases by 0.1
+    assert.ok(Math.abs(next.ox - 0.4) < 1e-6);
+    assert.equal(next.oy, 0.5);
+  });
+});