Implement AXIS parity UI and execution baseline

web/react/src/sourceAssets.ts

@@ -0,0 +1,6 @@
+// AXIS ships these exact 21/22/24px bitmap assets in the source tree.
+export const LINUXCNC_AXIS_ASSETS = "/linuxcnc/share/axis/images";
+
+export function axisIcon(name: string): string {
+  return `${LINUXCNC_AXIS_ASSETS}/${name}`;
+}