feat!: rewrite on Svelte 5, drop Phaser

Replace Phaser 3 with Svelte 5 as the rendering and UI layer. The
framework-agnostic core (level parser, board model, progress store,
microban level data) moves from src/game/core → src/lib/core with zero
code changes. Scenes and the hand-rolled button factory are gone; in
their place:

- src/App.svelte            root router (menu / levels / game)
- src/views/MenuView        title + play + progress + hints
- src/views/LevelSelectView paginated 5x4 grid with native <button>s
- src/views/GameView        owns BoardModel, handles input, HUD, win
- src/views/Board           purely presentational DOM renderer
- src/views/AppButton       shared themed wrapper for native <button>
- src/app.css               Nord palette ported to CSS variables

GameView uses a non-reactive BoardModel ref and syncs plain snapshot
fields (player, boxes, moves, won) into $state after every mutation —
Board consumes only plain props, so Svelte reactivity stays predictable
and the core class stays framework-agnostic. GameView is keyed on
levelIndex in App, so changing level remounts with fresh state.

Native <button> everywhere kills the click-hitbox class of bugs.
Animations are now CSS transform transitions (110ms) instead of tweens.

Bundle shrinks from ~1.5 MB Phaser to ~65 kB JS / 23 kB gzipped — about
60x smaller. Removed: phaser, terser, src/game, log.js (analytics
ping), phasermsg vite plugin, manual Phaser chunks, terser config,
public/style.css. Scripts simplified to dev/build.

Docs updated: codebase summary, architecture, code standards,
changelog, roadmap, README.

vite/config.dev.mjs

@@ -1,16 +1,9 @@
 import { defineConfig } from 'vite';
+import { svelte } from '@sveltejs/vite-plugin-svelte';
 
 export default defineConfig({
     base: './',
-    build: {
-        rollupOptions: {
-            output: {
-                manualChunks: {
-                    phaser: ['phaser']
-                }
-            }
-        },
-    },
+    plugins: [svelte()],
     server: {
         port: 8080
     }

vite/config.prod.mjs

@@ -1,47 +1,7 @@
 import { defineConfig } from 'vite';
-
-const phasermsg = () => {
-    return {
-        name: 'phasermsg',
-        buildStart() {
-            process.stdout.write(`Building for production...\n`);
-        },
-        buildEnd() {
-            const line = "---------------------------------------------------------";
-            const msg = `❤️❤️❤️ Tell us about your game! - games@phaser.io ❤️❤️❤️`;
-            process.stdout.write(`${line}\n${msg}\n${line}\n`);
-
-            process.stdout.write(`✨ Done ✨\n`);
-        }
-    }
-}
+import { svelte } from '@sveltejs/vite-plugin-svelte';
 
 export default defineConfig({
     base: '/sokoban/',
-    logLevel: 'warn',
-    build: {
-        rollupOptions: {
-            output: {
-                manualChunks: {
-                    phaser: ['phaser']
-                }
-            }
-        },
-        minify: 'terser',
-        terserOptions: {
-            compress: {
-                passes: 2
-            },
-            mangle: true,
-            format: {
-                comments: false
-            }
-        }
-    },
-    server: {
-        port: 8080
-    },
-    plugins: [
-        phasermsg()
-    ]
+    plugins: [svelte()]
 });