Address review: zoom, drag, clearance and pitchDeg for voice tilt

- A zoom during a pivoting tilt now scales the range the tilt holds,
  as it already did for orbit, instead of being undone on the next
  frame while reporting success. The zoom limits no longer move a view
  the wrong way: a zoom in leaves a view closer than 80 m in place, and
  a zoom out leaves an orbit beyond 5,000 km where it is.
- A grab, touch or wheel on the map while a voice fly-to is in flight
  drops the motion queued behind it. Cesium lands the flight anyway,
  so the orbit or tilt would otherwise take the camera back. Chained
  fly-tos in one reply keep the earliest snapshot.
- A pivot tilt toward the horizon stops lowering the camera at 150 m
  above the pivot and tilts the rest in place, so a close view no
  longer ends inside tiles or a hillside.
- pitchDeg is an absolute angle. A direction that contradicts it is
  refused, judged from the pitch the swing starts at, and the tool
  description says so.

src/cameraTilt.test.mjs

@@ -2,6 +2,7 @@ import assert from 'node:assert/strict';
 import test from 'node:test';
 import * as Cesium from 'cesium';
 import {
+  adjustOrbitRange,
   getActiveCameraMotion,
   initCameraVerbs,
   interruptCameraMotion,
@@ -222,3 +223,148 @@ test('a pivoting tilt yields when tracking takes the camera', (t) => {
   h.viewer.trackedEntityChanged.raiseEvent(entity);
   assert.equal(getActiveCameraMotion(), null);
 });
+
+/** Metres between the camera and the point it pivots about. */
+const pivotRange = (h) =>
+  Cesium.Cartesian3.distance(h.camera.positionWC, h.target);
+const heightM = (camera) =>
+  Cesium.Cartographic.fromCartesian(camera.positionWC).height;
+
+test('a zoom during a pivoting tilt changes the range it holds', (t) => {
+  const h = harness(t);
+  assert.equal(
+    moveCamera({ motion: 'tilt', direction: 'up', mode: 'continuous' }).ok,
+    true,
+  );
+  h.tick();
+  const before = pivotRange(h);
+  assert.equal(adjustOrbitRange(0.5), true, 'the tilt must take the zoom');
+  for (let i = 0; i < 5; i += 1) h.tick();
+  // The next frame's lookAt must not put the old range back.
+  assert.ok(
+    Math.abs(pivotRange(h) - before / 2) < 1,
+    `range ${pivotRange(h)} m, wanted ${before / 2} m`,
+  );
+});
+
+test('a zoom with no pivot to hold is left to the camera', (t) => {
+  harness(t, { pivot: false });
+  moveCamera({ motion: 'tilt', direction: 'up', mode: 'continuous' });
+  assert.equal(adjustOrbitRange(0.5), false);
+});
+
+test('a pivot tilt toward the horizon keeps its clearance above the ground', (t) => {
+  // A close top-down view: swinging 250 m of range to -5° would end ~22 m up.
+  const h = harness(t, { height: 250 });
+  assert.equal(moveCamera({ motion: 'tilt', pitchDeg: -5 }).ok, true);
+  let lowest = Infinity;
+  for (let i = 0; i < 600 && getActiveCameraMotion(); i += 1) {
+    h.tick();
+    lowest = Math.min(lowest, heightM(h.camera));
+  }
+  assert.equal(getActiveCameraMotion(), null, 'tilt must finish');
+  assert.ok(lowest > 149, `camera dropped to ${lowest} m`);
+  assert.ok(
+    Math.abs(pitchDeg(h.camera) - -5) < 0.5,
+    `pitch ${pitchDeg(h.camera)}`,
+  );
+  assert.ok(Cesium.Matrix4.equals(h.camera.transform, Cesium.Matrix4.IDENTITY));
+});
+
+test('a continuous tilt up from close in keeps its clearance', (t) => {
+  const h = harness(t, { height: 250 });
+  moveCamera({ motion: 'tilt', direction: 'up', mode: 'continuous' });
+  for (let i = 0; i < 600 && getActiveCameraMotion(); i += 1) {
+    h.tick();
+    assert.ok(heightM(h.camera) > 149, `camera at ${heightM(h.camera)} m`);
+  }
+  assert.ok(Math.abs(pitchDeg(h.camera) - -5) < 0.5);
+});
+
+test('a city-scale pivot tilt keeps the place centred to the horizon limit', (t) => {
+  const h = harness(t);
+  moveCamera({ motion: 'tilt', pitchDeg: -5 });
+  h.finish();
+  // 4 km of range clears the floor at every pitch: all pivot, no drift.
+  assert.ok(centreDrift(h) < 5, `centre drifted ${centreDrift(h)} m`);
+});
+
+test('pitchDeg against a contradicting direction is refused', (t) => {
+  harness(t, { pitch: -45 });
+  // "tilt down 10 degrees": -10° is an absolute angle, which is up from -45°.
+  const result = moveCamera({
+    motion: 'tilt',
+    direction: 'down',
+    pitchDeg: 10,
+  });
+  assert.equal(result.ok, false);
+  assert.match(result.error, /absolute angle/);
+  assert.equal(getActiveCameraMotion(), null);
+});
+
+test('pitchDeg with a direction that agrees still tilts', (t) => {
+  const h = harness(t, { pitch: -45 });
+  const result = moveCamera({
+    motion: 'tilt',
+    direction: 'down',
+    pitchDeg: -80,
+  });
+  assert.equal(result.ok, true);
+  assert.equal(result.direction, 'down');
+  h.finish();
+  assert.ok(Math.abs(pitchDeg(h.camera) - -80) < 0.5);
+});
+
+test('the pitchDeg and direction check uses the pitch the swing starts from', (t) => {
+  // At regional range the Earth curves away: the pivot pitch is a degree or
+  // two shallower than the camera's (-30°), so -29° is still down from it.
+  harness(t, { height: 150000, pitch: -30 });
+  const up = moveCamera({ motion: 'tilt', direction: 'up', pitchDeg: -29 });
+  assert.equal(up.ok, false);
+  assert.match(up.error, /tilts down, not up/);
+  const down = moveCamera({ motion: 'tilt', direction: 'down', pitchDeg: -29 });
+  assert.equal(down.ok, true);
+  assert.equal(down.direction, 'down');
+});
+
+test('after a zoom in, a pivoting tilt never lowers the camera further', (t) => {
+  const h = harness(t, { height: 1000 });
+  moveCamera({ motion: 'tilt', direction: 'up', mode: 'continuous' });
+  while (pitchDeg(h.camera) < -30) h.tick();
+  adjustOrbitRange(1 / 2.4);
+  adjustOrbitRange(1 / 2.4);
+  h.tick();
+  const afterZoom = heightM(h.camera);
+  for (let i = 0; i < 600 && getActiveCameraMotion(); i += 1) {
+    h.tick();
+    assert.ok(
+      heightM(h.camera) > afterZoom - 1,
+      `camera fell from ${afterZoom} m to ${heightM(h.camera)} m`,
+    );
+  }
+  assert.ok(Math.abs(pitchDeg(h.camera) - -5) < 0.5);
+});
+
+test('a zoom in during a close pivot tilt never pushes the camera out', (t) => {
+  // 62 m of range, under the 80 m zoom floor.
+  const h = harness(t, { height: 40, pitch: -40 });
+  moveCamera({ motion: 'tilt', direction: 'down', mode: 'continuous' });
+  h.tick();
+  const before = pivotRange(h);
+  assert.ok(before < 80, `range ${before} m`);
+  adjustOrbitRange(1 / 1.6);
+  h.tick();
+  assert.ok(pivotRange(h) <= before + 0.01, `range grew to ${pivotRange(h)} m`);
+});
+
+test('a zoom out during a far orbit never pulls the camera in', (t) => {
+  // 15,000 km up, beyond the 5,000 km zoom cap.
+  const h = harness(t, { height: 15_000_000 });
+  assert.equal(moveCamera({ motion: 'orbit', mode: 'continuous' }).ok, true);
+  h.tick();
+  const before = pivotRange(h);
+  assert.ok(before > 5_000_000, `range ${before} m`);
+  assert.equal(adjustOrbitRange(2.4), true);
+  h.tick();
+  assert.ok(pivotRange(h) >= before - 1, `range fell to ${pivotRange(h)} m`);
+});