fix(cctv): on a globe map the camera plane ends where the view meets the ground

The activation probe raycast only the photoreal tiles. On a globe map the ray
missed, or ran on through the Earth and met a primitive thousands of
kilometres away, and the monitor plane stood at the camera's full range:
about a kilometre wide and hundreds of metres up. A hit at or beyond the range
now counts as none, and on a globe map the plane also clamps short of the
globe's terrain along the axis, or flat ground at the mount's ground while
that terrain is still loading, whichever is nearer.

src/data/cctv.test.mjs

@@ -35,6 +35,7 @@ import cctvLayer, {
   _pushAmbientCardEntriesForTest,
   _setCctvOverlayHostForTest,
   activationProbeClampRange,
+  flatGroundAxisDistance,
   bindCctvWorldClickGesture,
   clearProbeClampOnDeactivation,
   computeFrustumGeometry,
@@ -655,6 +656,17 @@ test('activation obstruction clamp uses the field-derived 12 m floor', () => {
   assert.equal(activationProbeClampRange(210, 250), null);
 });
 
+test('on a globe map the axis ends on flat ground at the mount ground', () => {
+  // A 24 m mount pitched 30° down meets the ground 48 m along its axis.
+  assert.ok(Math.abs(flatGroundAxisDistance(24, -30) - 48) < 1e-9);
+  // The default 700 m range then clamps just short of that, not 700 m out.
+  const clamp = activationProbeClampRange(700, flatGroundAxisDistance(24, -30));
+  assert.ok(Math.abs(clamp - 44) < 1e-9);
+  assert.equal(flatGroundAxisDistance(24, 0), null);
+  assert.equal(flatGroundAxisDistance(24, 10), null);
+  assert.equal(flatGroundAxisDistance(0, -30), null);
+});
+
 test('deactivation clears the probe clamp and restores nominal frustum geometry', () => {
   const record = {
     camera: { ...UNCLAMPED_CAMERA },