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/extend-config.ts

@@ -0,0 +1,53 @@
+import fs from "node:fs";
+import { homedir } from "node:os";
+import path from "node:path";
+import type { ExtendConfig } from "./types.js";
+
+function extractYamlFrontMatter(content: string): string | null {
+  const match = content.match(/^---\s*\n([\s\S]*?)\n---\s*$/m);
+  return match ? match[1]! : null;
+}
+
+function parseExtendYaml(yaml: string): Partial<ExtendConfig> {
+  const config: Partial<ExtendConfig> = {};
+  for (const line of yaml.split("\n")) {
+    const trimmed = line.trim();
+    if (!trimmed || trimmed.startsWith("#")) continue;
+    const colonIdx = trimmed.indexOf(":");
+    if (colonIdx < 0) continue;
+    const key = trimmed.slice(0, colonIdx).trim();
+    let value = trimmed.slice(colonIdx + 1).trim().replace(/^['"]|['"]$/g, "");
+    if (value === "null" || value === "") continue;
+
+    if (key === "default_theme") config.default_theme = value;
+    else if (key === "default_color") config.default_color = value;
+    else if (key === "default_font_family") config.default_font_family = value;
+    else if (key === "default_font_size") config.default_font_size = value.endsWith("px") ? value : `${value}px`;
+    else if (key === "default_code_theme") config.default_code_theme = value;
+    else if (key === "mac_code_block") config.mac_code_block = value === "true";
+    else if (key === "show_line_number") config.show_line_number = value === "true";
+    else if (key === "cite") config.cite = value === "true";
+    else if (key === "count") config.count = value === "true";
+    else if (key === "legend") config.legend = value;
+    else if (key === "keep_title") config.keep_title = value === "true";
+  }
+  return config;
+}
+
+export function loadExtendConfig(): Partial<ExtendConfig> {
+  const paths = [
+    path.join(process.cwd(), ".baoyu-skills", "baoyu-markdown-to-html", "EXTEND.md"),
+    path.join(homedir(), ".baoyu-skills", "baoyu-markdown-to-html", "EXTEND.md"),
+  ];
+  for (const p of paths) {
+    try {
+      const content = fs.readFileSync(p, "utf-8");
+      const yaml = extractYamlFrontMatter(content);
+      if (!yaml) continue;
+      return parseExtendYaml(yaml);
+    } catch {
+      continue;
+    }
+  }
+  return {};
+}