feat(js): m09 input, app, runtime, browser, main, index.html and smoke test

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

js/src/input.js

@@ -0,0 +1,8 @@
+import { todo } from './todo.js'
+
+/**
+ * Translate a keyboard key name (as in `KeyboardEvent.key`) into the game action it triggers, or `null`.
+ * `ArrowUp`/`w`/`W` -> `Action.Turn('Up')`, `ArrowDown`/`s`/`S` -> Down, `ArrowLeft`/`a`/`A` -> Left,
+ * `ArrowRight`/`d`/`D` -> Right. Any other key -> `null`.
+ */
+export const keyToAction = (key) => todo('m09')