Add curl-friendly /api/convert endpoint

Accepts raw markdown body, format via query param:
  curl --data-binary @file.md host/api/convert > out.html
  curl --data-binary @file.md host/api/convert?format=pdf -o out.pdf

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server.js

@@ -237,6 +237,43 @@ const server = http.createServer(async (req, res) => {
     return;
   }
 
+  // curl-friendly API: accepts raw markdown body, format via query param or Accept header
+  // Usage:
+  //   curl -X POST --data-binary @file.md https://host/api/convert > output.html
+  //   curl -X POST --data-binary @file.md https://host/api/convert?format=pdf -o output.pdf
+  if (req.method === "POST" && req.url.startsWith("/api/convert")) {
+    try {
+      const url = new URL(req.url, `http://${req.headers.host}`);
+      const formatParam = url.searchParams.get("format") || "html";
+      const markdown = await parseBody(req);
+
+      if (!markdown.trim()) {
+        res.writeHead(400, { "Content-Type": "text/plain" });
+        res.end("Empty body — POST raw markdown text");
+        return;
+      }
+
+      const html = markdownToHtml(markdown);
+
+      if (formatParam === "pdf") {
+        const pdfBuffer = await htmlToPdf(html);
+        res.writeHead(200, {
+          "Content-Type": "application/pdf",
+          "Content-Disposition": "attachment; filename=output.pdf",
+        });
+        res.end(pdfBuffer);
+      } else {
+        res.writeHead(200, { "Content-Type": "text/html; charset=utf-8" });
+        res.end(html);
+      }
+    } catch (err) {
+      console.error("API convert error:", err);
+      res.writeHead(500, { "Content-Type": "text/plain" });
+      res.end("Conversion failed: " + err.message);
+    }
+    return;
+  }
+
   if (req.method === "GET" && req.url === "/health") {
     res.writeHead(200, { "Content-Type": "application/json" });
     res.end(JSON.stringify({ status: "ok" }));