Remove shiki shim — handled by forked vue-stream-markdown

The fork inlines shiki stubs at build time, so consumers no longer
need to alias shiki to a shim.

src/shims/shiki.ts

@@ -1,12 +0,0 @@
-export const bundledThemesInfo: never[] = []
-export const bundledLanguagesInfo: never[] = []
-export async function createHighlighter() {
-  return {
-    getLoadedLanguages: () => [] as string[],
-    getLoadedThemes: () => [] as string[],
-    codeToTokens: () => ({ tokens: [], themeName: '', fg: '', bg: '' }),
-    loadLanguage: async () => {},
-    loadTheme: async () => {},
-    dispose: () => {}
-  }
-}

vite.config.ts

@@ -18,9 +18,8 @@ export default defineConfig(async () => ({
   resolve: {
     alias: {
       '@': resolve(__dirname, 'src'),
-      // vue-stream-markdown eagerly loads these optional peer deps on mount.
+      // vue-stream-markdown eagerly loads mermaid/beautiful-mermaid as optional peer deps.
       // Alias to empty shims to avoid runtime errors and reduce bundle size.
-      shiki: resolve(__dirname, 'src/shims/shiki.ts'),
       mermaid: resolve(__dirname, 'src/shims/mermaid.ts'),
       'beautiful-mermaid': resolve(__dirname, 'src/shims/mermaid.ts')
     }