feat: WASM web app (browser LesS/KEY) backed by the hel core

Run the real hel core in the browser via WebAssembly, replacing the plain-JS
ooke.github.io/sk reimplementation so the web and the CLI share one generator.

- hel core: new storage module (native fs / wasm localStorage) backs
  init/source/dump/correct; the pipe and pb branches are gated out of wasm;
  the wasm editor is completed (EditorRef) and its password prompt no longer
  blocks the single JS thread (synchronous hel_get_password instead of a
  thread::sleep poll).
- helwasm: hel_load_script for bulk import, a panic hook in hel_init, dropped
  the ok_add / web-sys leftovers; build.sh runs wasm-bindgen into a committed
  pkg/ so GitHub Pages can serve the static dir with no CI.
- UI: rewritten index.html + style.css in the kaizenkodo.org style — responsive,
  masked-but-copyable passwords with click-to-reveal, a quick-generate card plus
  a full command console, localStorage persistence, and paste import/export.

helwasm/pkg/helwasm_bg.wasm.d.ts

@@ -0,0 +1,11 @@
+/* tslint:disable */
+/* eslint-disable */
+export const memory: WebAssembly.Memory;
+export const hel_command: (a: number, b: number) => [number, number];
+export const hel_init: () => void;
+export const hel_load_script: (a: number, b: number) => [number, number];
+export const __wbindgen_free: (a: number, b: number, c: number) => void;
+export const __wbindgen_malloc: (a: number, b: number) => number;
+export const __wbindgen_realloc: (a: number, b: number, c: number, d: number) => number;
+export const __wbindgen_externrefs: WebAssembly.Table;
+export const __wbindgen_start: () => void;