fix(rail): focusTrain refuses a train the layer does not draw

A ride let go with restore focuses its train again. When the train's
category was turned off during the ride, or for a copy another feed draws,
focusTrain selected and followed a train with no marker. It now returns
false for a train in a category turned off or hidden as another feed's
copy, and leaves the selection and the camera as they are.

src/layers/rail/cockpitSubject.js

@@ -299,10 +299,12 @@ export function createRailCockpitSubject({
     /**
      * Select the train `key` and hand it the camera, as a click on it does.
      * @param {string} key
-     * @returns {boolean} False for a train the layer does not show.
+     * @returns {boolean} False for a train the layer does not show: gone, in
+     *   a category turned off, or a copy another feed draws (dedupe.js).
      */
     focusTrain(key) {
-      if (!state._trains.has(key)) return false;
+      const entry = state._trains.get(key);
+      if (!entry || !parts.rendering.categoryShown(entry)) return false;
       parts.selection.selectAndFocusTrain(key);
       return true;
     },

src/layers/rail/cockpitSubject.test.mjs

@@ -290,6 +290,9 @@ test('a held train stays the copy drawn when another feed’s copy outranks it,
     1,
     'its card',
   );
+  // The copy hidden is not focused: the selection stays on the one drawn.
+  assert.equal(app.layer.focusTrain(a), false);
+  assert.equal(app.state()._selectedKey, b);
 
   // A hold of the copy hidden draws it at once, in place of the other.
   assert.equal(app.layer.setCockpitSubject(a), true);
@@ -343,6 +346,27 @@ test('a held train keeps the selection and moves, hidden, when its category is t
   assert.ok(app.state()._moving.has(app.entry(T1)), 'playing again');
 });
 
+test('a ride let go with restore does not focus a train its category hides', async (t) => {
+  const app = await onTheLine(t);
+  // The documented provider: hold on entry; on exit, release, then focus
+  // the train again when asked to restore.
+  assert.equal(app.layer.setCockpitSubject(T1), true);
+  app.layer.setParams({ regional: false });
+  app.layer.setCockpitSubject(null);
+  assert.equal(app.layer.focusTrain(T1), false, 'not drawn');
+  assert.equal(app.state()._selectedKey, null, 'not selected');
+  assert.equal(app.parts().follow.stats(), null, 'not followed');
+  assert.equal(app.viewer.trackedEntity, undefined);
+  assert.equal(app.focusRequests.length, 0, 'not flown to');
+  assert.equal(app.entry(T1).marker.show, false);
+
+  // Shown again, it focuses as before.
+  app.layer.setParams({ regional: true });
+  assert.equal(app.layer.focusTrain(T1), true);
+  assert.equal(app.state()._selectedKey, T1);
+  assert.ok(app.parts().follow.isFollowing(T1), 'the camera is handed to it');
+});
+
 test('a held train that goes takes the hold with it; focusTrain selects', async (t) => {
   const app = await onTheLine(t);
   app.layer.setCockpitSubject(T1);