Fix voice camera tilt from a top-down view

A voice fly-to frames a city top-down, at pitch -90. The tilt clamp
rejected any step that left the pitch below -89, so the first frame of
"tilt up" stopped the motion and "tilt down" was refused: from the view
voice lands on, no tilt ever moved the camera. A bare "tilt the camera"
also failed because tilt required a direction.

- Clamp tilt only in the direction of travel, so -90 can tilt up.
- Swing the camera about the ground under the crosshair, so the place
  stays centred and the heading is kept. A tracked view still tilts in
  place, and a pivot tilt yields when tracking takes the camera.
- Add an optional move_camera pitchDeg for "tilt 45 degrees"; a tilt
  with neither angle nor direction settles at -45 (oblique view).
- Re-derive the voice tool schema pins for the new argument and wording,
  and keep the Realtime prompt under its 52,000-character budget.

src/cameraTilt.test.mjs

@@ -0,0 +1,224 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import * as Cesium from 'cesium';
+import {
+  getActiveCameraMotion,
+  initCameraVerbs,
+  interruptCameraMotion,
+  moveCamera,
+} from './cameraVerbs.js';
+
+const radians = Cesium.Math.toRadians;
+const degrees = Cesium.Math.toDegrees;
+
+/** Real Cesium camera over London with no renderer: the voice fly-to frame. */
+function harness(
+  t,
+  { height = 4000, heading = 0, pitch = -90, pivot = true } = {},
+) {
+  const realPerformance = globalThis.performance;
+  let nowMs = 0;
+  globalThis.performance = { now: () => nowMs };
+  const canvas = Object.assign(new EventTarget(), {
+    clientWidth: 1280,
+    clientHeight: 800,
+    width: 1280,
+    height: 800,
+  });
+  const ellipsoid = Cesium.Ellipsoid.WGS84;
+  const scene = {
+    canvas,
+    drawingBufferWidth: 1280,
+    drawingBufferHeight: 800,
+    frameState: { mode: Cesium.SceneMode.SCENE3D },
+    mapProjection: new Cesium.GeographicProjection(ellipsoid),
+    globe: { ellipsoid },
+    mapMode2D: Cesium.MapMode2D.INFINITE_SCROLL,
+    mode: Cesium.SceneMode.SCENE3D,
+    pixelRatio: 1,
+    tweens: [],
+    requestRender() {},
+  };
+  const camera = new Cesium.Camera(scene);
+  scene.camera = camera;
+  camera.setView({
+    destination: Cesium.Cartesian3.fromDegrees(-0.1276, 51.5072, height),
+    orientation: { heading: radians(heading), pitch: radians(pitch), roll: 0 },
+  });
+  const viewer = {
+    camera,
+    scene,
+    trackedEntity: undefined,
+    trackedEntityChanged: new Cesium.Event(),
+    clock: { onTick: new Cesium.Event() },
+  };
+  // The app's view target: the ground point under the screen centre.
+  const viewTarget = () => {
+    const ray = new Cesium.Ray(camera.positionWC, camera.directionWC);
+    const hit = Cesium.IntersectionTests.rayEllipsoid(ray, ellipsoid);
+    return hit ? Cesium.Ray.getPoint(ray, hit.start) : undefined;
+  };
+  const target = viewTarget();
+  initCameraVerbs(viewer, pivot ? viewTarget : () => undefined);
+  t.after(() => {
+    interruptCameraMotion('test-cleanup');
+    globalThis.performance = realPerformance;
+  });
+  const tick = (seconds = 1 / 30) => {
+    nowMs += seconds * 1000;
+    viewer.clock.onTick.raiseEvent(viewer.clock);
+  };
+  const finish = () => {
+    for (let i = 0; i < 600 && getActiveCameraMotion(); i += 1) tick();
+    assert.equal(getActiveCameraMotion(), null, 'tilt must finish');
+  };
+  return { viewer, camera, target, tick, finish, viewTarget };
+}
+
+const pitchDeg = (camera) => degrees(camera.pitch);
+const headingDeg = (camera) =>
+  degrees(Cesium.Math.negativePiToPi(camera.heading));
+
+/** Metres between the original centre and the ground now under the crosshair. */
+function centreDrift(h) {
+  return Cesium.Cartesian3.distance(h.viewTarget(), h.target);
+}
+
+test('tilt up leaves a top-down view and keeps the place centred', (t) => {
+  const h = harness(t);
+  const result = moveCamera({ motion: 'tilt', direction: 'up' });
+  assert.equal(result.ok, true);
+  h.finish();
+  assert.ok(
+    Math.abs(pitchDeg(h.camera) - -75) < 0.5,
+    `pitch ${pitchDeg(h.camera)}`,
+  );
+  assert.ok(centreDrift(h) < 5, `centre drifted ${centreDrift(h)} m`);
+  assert.ok(Cesium.Matrix4.equals(h.camera.transform, Cesium.Matrix4.IDENTITY));
+});
+
+test('continuous tilt up from top-down keeps moving', (t) => {
+  const h = harness(t);
+  assert.equal(
+    moveCamera({ motion: 'tilt', direction: 'up', mode: 'continuous' }).ok,
+    true,
+  );
+  for (let i = 0; i < 30; i += 1) h.tick();
+  assert.equal(getActiveCameraMotion()?.kind, 'tilt');
+  assert.ok(pitchDeg(h.camera) > -82, `pitch ${pitchDeg(h.camera)}`);
+});
+
+test('a requested angle tilts to that pitch', (t) => {
+  const h = harness(t);
+  const result = moveCamera({ motion: 'tilt', pitchDeg: -45 });
+  assert.equal(result.ok, true);
+  assert.equal(result.direction, 'up');
+  assert.equal(result.pitchDeg, -45);
+  h.finish();
+  assert.ok(
+    Math.abs(pitchDeg(h.camera) - -45) < 0.5,
+    `pitch ${pitchDeg(h.camera)}`,
+  );
+  assert.ok(centreDrift(h) < 5, `centre drifted ${centreDrift(h)} m`);
+});
+
+test('a bare tilt settles on the default oblique angle', (t) => {
+  const h = harness(t);
+  const result = moveCamera({ motion: 'tilt' });
+  assert.equal(result.ok, true);
+  assert.equal(result.pitchDeg, -45);
+  h.finish();
+  assert.ok(Math.abs(pitchDeg(h.camera) - -45) < 0.5);
+});
+
+test('a requested angle can tilt back down toward top-down', (t) => {
+  const h = harness(t, { pitch: -30 });
+  const result = moveCamera({ motion: 'tilt', pitchDeg: -80 });
+  assert.equal(result.direction, 'down');
+  h.finish();
+  assert.ok(Math.abs(pitchDeg(h.camera) - -80) < 0.5);
+});
+
+test('requested angles clamp to the tilt limits', (t) => {
+  const h = harness(t);
+  assert.equal(moveCamera({ motion: 'tilt', pitchDeg: -2 }).pitchDeg, -5);
+  h.finish();
+  assert.ok(Math.abs(pitchDeg(h.camera) - -5) < 0.5);
+});
+
+test('a positive angle is read as the same angle below the horizon', (t) => {
+  const h = harness(t);
+  assert.equal(moveCamera({ motion: 'tilt', pitchDeg: 45 }).pitchDeg, -45);
+  h.finish();
+  assert.ok(Math.abs(pitchDeg(h.camera) - -45) < 0.5);
+});
+
+for (const pitch of ['', null, false, ' ', 'steep'])
+  test(`a blank or non-numeric angle ${JSON.stringify(pitch)} is ignored`, (t) => {
+    harness(t);
+    const result = moveCamera({ motion: 'tilt', pitchDeg: pitch });
+    // No angle and no direction: the default oblique view, never the horizon.
+    assert.equal(result.pitchDeg, -45);
+  });
+
+test('a requested angle the camera already holds is a no-op', (t) => {
+  harness(t, { pitch: -45 });
+  const result = moveCamera({ motion: 'tilt', pitchDeg: -45 });
+  assert.equal(result.ok, true);
+  assert.equal(result.unchanged, true);
+  assert.equal(getActiveCameraMotion(), null);
+});
+
+test('tilt down from top-down still refuses honestly', (t) => {
+  harness(t);
+  const result = moveCamera({ motion: 'tilt', direction: 'down' });
+  assert.equal(result.ok, false);
+  assert.match(result.error, /straight down/);
+});
+
+test('a tilt up nudge stops at the horizon limit', (t) => {
+  const h = harness(t, { pitch: -12 });
+  assert.equal(moveCamera({ motion: 'tilt', direction: 'up' }).ok, true);
+  h.finish();
+  assert.ok(Math.abs(pitchDeg(h.camera) - -5) < 0.5);
+});
+
+test('without a ground pivot a tilt still leaves top-down in place', (t) => {
+  const h = harness(t, { pivot: false });
+  const before = Cesium.Cartesian3.clone(h.camera.positionWC);
+  assert.equal(moveCamera({ motion: 'tilt', direction: 'up' }).ok, true);
+  h.finish();
+  assert.ok(Math.abs(pitchDeg(h.camera) - -75) < 0.5);
+  assert.ok(Cesium.Cartesian3.distance(h.camera.positionWC, before) < 1e-6);
+});
+
+for (const heading of [0, 30, -120])
+  test(`tilt from top-down keeps the ${heading}° heading`, (t) => {
+    const h = harness(t, { heading, height: 67000 });
+    // Top-down float noise must not pick a new heading for the pivot.
+    assert.equal(moveCamera({ motion: 'tilt', pitchDeg: -45 }).ok, true);
+    h.finish();
+    assert.ok(
+      Math.abs(headingDeg(h.camera) - heading) < 1,
+      `heading ${headingDeg(h.camera)}`,
+    );
+    assert.ok(centreDrift(h) < 50, `centre drifted ${centreDrift(h)} m`);
+  });
+
+test('an oblique tilt keeps its heading toward the pivot', (t) => {
+  const h = harness(t, { heading: 75, pitch: -60 });
+  assert.equal(moveCamera({ motion: 'tilt', pitchDeg: -30 }).ok, true);
+  h.finish();
+  assert.ok(Math.abs(headingDeg(h.camera) - 75) < 0.5);
+  assert.ok(centreDrift(h) < 5, `centre drifted ${centreDrift(h)} m`);
+});
+
+test('a pivoting tilt yields when tracking takes the camera', (t) => {
+  const h = harness(t);
+  assert.equal(moveCamera({ motion: 'tilt', pitchDeg: -45 }).ok, true);
+  h.tick();
+  const entity = { id: 'tracked' };
+  h.viewer.trackedEntity = entity;
+  h.viewer.trackedEntityChanged.raiseEvent(entity);
+  assert.equal(getActiveCameraMotion(), null);
+});