fix bug where buildings could not output directly on splitters

src/test/BeltSystemTest.cpp

@@ -629,6 +629,24 @@ TEST_CASE("BeltSystem: splitter accepts new items after building pulls from fron
     REQUIRE(bs.peekItem(Port{tileSpl, Rotation::South}).has_value());
 }
 
+TEST_CASE("BeltSystem: tryPutItem succeeds directly on a splitter tile", "[belt]")
+{
+    // Regression: buildings outputting onto a splitter tile were silently dropped
+    // because tryPutItem had no splitter case and returned false.
+    BeltSystem bs(kFastBeltSpeed);
+
+    const QPoint tileSpl(0, 0);
+    bs.placeSplitter(tileSpl, Rotation::North, Rotation::South);
+
+    REQUIRE(bs.tryPutItem(tileSpl, makeItem("iron_ore"), Rotation::East));
+
+    // Item should arrive at one of the output fronts after the splitter ticks through.
+    bs.tick();   // back advances to 0.5, routes to frontA
+    bs.tick();   // frontA reaches 1.0
+
+    REQUIRE(bs.peekItem(Port{tileSpl, Rotation::North}).has_value());
+}
+
 TEST_CASE("BeltSystem: splitter alternates between two unregistered outputs (building inputs)", "[belt]")
 {
     BeltSystem bs(kFastBeltSpeed);