feat: add bidirectional ttf/otf/woff font converter

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/converters/font.js

@@ -0,0 +1,39 @@
+import fs from 'node:fs/promises';
+import { Font } from 'fonteditor-core';
+import opentype from 'opentype.js';
+import { register } from './registry.js';
+
+const FONT_FORMATS = ['ttf', 'otf', 'woff'];
+
+export async function convertBufferToOtf(buffer, outputPath) {
+  const ab = buffer.buffer.slice(buffer.byteOffset, buffer.byteOffset + buffer.byteLength);
+  const font = opentype.parse(ab);
+  await fs.writeFile(outputPath, Buffer.from(font.toArrayBuffer()));
+}
+
+async function convertViaFontEditor(inputPath, outputPath, sourceFormat, targetFormat) {
+  const buffer = await fs.readFile(inputPath);
+  const font = Font.create(buffer, { type: sourceFormat });
+  const out = font.write({ type: targetFormat });
+  await fs.writeFile(outputPath, Buffer.from(out));
+}
+
+export function registerFontConverter() {
+  for (const sourceFormat of FONT_FORMATS) {
+    for (const targetFormat of FONT_FORMATS) {
+      if (sourceFormat === targetFormat) continue;
+      register({
+        family: 'font',
+        sourceFormat,
+        targetFormat,
+        convert: async (inputPath, outputPath) => {
+          if (targetFormat === 'otf') {
+            await convertBufferToOtf(await fs.readFile(inputPath), outputPath);
+          } else {
+            await convertViaFontEditor(inputPath, outputPath, sourceFormat, targetFormat);
+          }
+        },
+      });
+    }
+  }
+}