The code moves into src/: index, server and the test harness keep the root

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/dom.js

@@ -0,0 +1,6 @@
+// Canvas handles — imported by everyone, imports nothing (keeps module cycles harmless).
+export const cv = document.getElementById('c');
+// alpha:false — render() clears the whole frame to an opaque colour anyway, so declaring the canvas
+// opaque lets the compositor skip blending a 2.5-megapixel layer 60 times a second (battery, not
+// looks). desynchronized is a further no-op-where-unsupported compositor shortcut (Chrome).
+export const ctx = cv.getContext('2d', { alpha: false, desynchronized: true });