fix(cockpit): a ship's double-click memory belongs to that ship

The first press's picture of the ship survived a change of followed
subject: following an aircraft (or another ship) within 700 ms let a
double-click on the old ship's spot enter the new subject. The memory now
carries the ship's MMSI and is used only while that ship is still the one
followed.

src/ui/cockpitBridge.test.mjs

@@ -1435,6 +1435,28 @@ test('a followed aircraft keeps its own double-click hit area', async (t) => {
   assert.equal(cockpit.active, false);
 });
 
+test("a ship's double-click memory does not carry over to an aircraft followed since", async (t) => {
+  const aircraftInfo = {
+    icao24: 'abc123',
+    callsign: 'TEST1',
+    latitude: 54.5,
+    longitude: 10.2,
+    altitudeM: 3000,
+    velocityMps: 200,
+    track: 45,
+    onGround: false,
+  };
+  const { cockpit, viewer, aircraft } = fixture(t, { aircraftInfo });
+  heightSensitiveProjection(viewer);
+  // The press finds the ship at (400, 300).
+  cockpit.onScenePointerDown(1000);
+  // Within the memory, an aircraft is followed, drawn elsewhere.
+  viewer.trackedEntity = aircraft;
+  heightSensitiveProjection(viewer, { x: 900 });
+  assert.equal(cockpit.onSceneDoubleClick({ x: 400, y: 300 }, 1250), false);
+  assert.equal(cockpit.active, false);
+});
+
 test("a double-click's second press keeps the first press's picture of the ship", async (t) => {
   const { cockpit, viewer, store } = fixture(t);
   heightSensitiveProjection(viewer);

src/ui/cockpitInput.js

@@ -81,7 +81,8 @@ export function onScenePointerDown(nowMs = performance.now()) {
     return;
   }
   const at = subjectCanvasPosition.call(this);
-  this.doubleClickStart = at ? { x: at.x, y: at.y, atMs: nowMs } : null;
+  const mmsi = this.readVesselInfo()?.mmsi ?? null;
+  this.doubleClickStart = at ? { x: at.x, y: at.y, atMs: nowMs, mmsi } : null;
 }
 
 /**
@@ -105,6 +106,10 @@ export function onSceneDoubleClick(position, nowMs = performance.now()) {
     doubleClickHitsSubject(position, subjectCanvasPosition.call(this)) ||
     (Boolean(start) &&
       nowMs - start.atMs <= DOUBLE_CLICK_MEMORY_MS &&
+      // The memory is the ship's it was taken for: one followed since (an
+      // aircraft, another ship) is hit only where it is drawn.
+      this.resolveEntryKind() === 'vessel' &&
+      start.mmsi === (this.readVesselInfo()?.mmsi ?? null) &&
       doubleClickHitsSubject(position, start));
   if (!hit) return false;
   this.enter();