feat(baoyu-markdown-to-html): modularize render.ts and bundle code themes locally

Split monolithic render.ts into cli, constants, extend-config, html-builder, renderer, themes, and types modules. Bundle highlight.js code theme CSS files locally instead of CDN loading.

skills/baoyu-markdown-to-html/scripts/md/themes.ts

@@ -0,0 +1,62 @@
+import fs from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import type { ThemeName } from "./types.js";
+
+const SCRIPT_DIR = path.dirname(fileURLToPath(import.meta.url));
+export const THEME_DIR = path.resolve(SCRIPT_DIR, "themes");
+const FALLBACK_THEMES: ThemeName[] = ["default", "grace", "simple"];
+
+function stripOutputScope(cssContent: string): string {
+  let css = cssContent;
+  css = css.replace(/#output\s*\{/g, "body {");
+  css = css.replace(/#output\s+/g, "");
+  css = css.replace(/^#output\s*/gm, "");
+  return css;
+}
+
+function discoverThemesFromDir(dir: string): string[] {
+  if (!fs.existsSync(dir)) {
+    return [];
+  }
+  return fs
+    .readdirSync(dir)
+    .filter((name) => name.endsWith(".css"))
+    .map((name) => name.replace(/\.css$/i, ""))
+    .filter((name) => name.toLowerCase() !== "base");
+}
+
+function resolveThemeNames(): ThemeName[] {
+  const localThemes = discoverThemesFromDir(THEME_DIR);
+  const resolved = localThemes.filter((name) =>
+    fs.existsSync(path.join(THEME_DIR, `${name}.css`))
+  );
+  return resolved.length ? resolved : FALLBACK_THEMES;
+}
+
+export const THEME_NAMES: ThemeName[] = resolveThemeNames();
+
+export function loadThemeCss(theme: ThemeName): {
+  baseCss: string;
+  themeCss: string;
+} {
+  const basePath = path.join(THEME_DIR, "base.css");
+  const themePath = path.join(THEME_DIR, `${theme}.css`);
+
+  if (!fs.existsSync(basePath)) {
+    throw new Error(`Missing base CSS: ${basePath}`);
+  }
+
+  if (!fs.existsSync(themePath)) {
+    throw new Error(`Missing theme CSS for "${theme}": ${themePath}`);
+  }
+
+  return {
+    baseCss: fs.readFileSync(basePath, "utf-8"),
+    themeCss: fs.readFileSync(themePath, "utf-8"),
+  };
+}
+
+export function normalizeThemeCss(css: string): string {
+  return stripOutputScope(css);
+}