feat(scala): m09 input/app/runtime and m10 extensions with tests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scala/test/M09Input.test.scala

@@ -0,0 +1,10 @@
+package snake
+
+import Fixtures.*
+
+class M09InputSuite extends munit.FunSuite:
+  cases("m09-input").foreach { c =>
+    test(s"keyToAction: ${c("name").str}") {
+      assertEquals(Input.keyToAction(c("args")(0).str), opt(c("expected"))(action))
+    }
+  }