Take TTC vehicle mode from the fleet number before the route

Replacement buses on 5xx streetcar routes were drawn as streetcars, and
Flexity streetcars reporting no route were drawn as buses. A feed can now
supply vehicleMode(id); TTC maps 4400-4699 to streetcars and every other
fleet number to buses, falling back to the route otherwise.

server/providers/transitHistory.test.mjs

@@ -179,3 +179,26 @@ test('snapshot capacity pressure preserves members not yet visited and discloses
   assert.equal(recreated.fixes.length, 1);
   assert.equal(recreated.truncated, true);
 });
+test('a feed fleet-number mode outranks its route mode in the epoch context', (t) => {
+  const h = history(t);
+  const ttc = {
+    id: 'ttc',
+    historyRetention: true,
+    defaultMode: 'bus',
+    routeMode: (route) => (/^5\d\d$/.test(route ?? '') ? 'tram' : 'bus'),
+    vehicleMode: (id) =>
+      /^4[4-6]\d\d$/.test(id) ? 'tram' : /^\d{4}$/.test(id) ? 'bus' : 'unknown',
+  };
+  h.ingest(
+    ttc,
+    [
+      row(100000, '8515', { routeId: '506' }),
+      row(100000, '4507', { routeId: null }),
+      row(100000, 'x1', { routeId: '501' }),
+    ],
+    100000,
+  );
+  assert.equal(h.get('ttc', '8515', 100000).epochs[0].mode, 'bus');
+  assert.equal(h.get('ttc', '4507', 100000).epochs[0].mode, 'tram');
+  assert.equal(h.get('ttc', 'x1', 100000).epochs[0].mode, 'tram');
+});