feat(ascii-art): figlet adapter with lazy load, font cache, structured error

src/main/AsciiArt.figlet-adapter.js

@@ -0,0 +1,71 @@
+/**
+ * Figlet adapter — lazy-loads the figlet package and caches the font list.
+ *
+ * The figlet npm package ships ~400 fonts. Lazy-loading on first
+ * `generateFiglet` / `listFigletFonts` call keeps app startup fast. If
+ * `require('figlet')` itself fails (corrupt install), the adapter reports
+ * the system as unavailable instead of crashing.
+ *
+ * @module AsciiArt.figlet-adapter
+ */
+'use strict';
+
+class AsciiArtFigletError extends Error {
+  constructor(message, cause) {
+    super(message);
+    this.name = 'AsciiArtFigletError';
+    this.cause = cause;
+  }
+}
+
+let _figlet = undefined; // undefined = not yet attempted; null = failed
+let _figletFonts = undefined; // undefined = not yet listed
+
+function loadFiglet() {
+  if (_figlet !== undefined) return _figlet;
+  try {
+    _figlet = require('figlet');
+  } catch {
+    _figlet = null;
+  }
+  return _figlet;
+}
+
+function listFigletFonts() {
+  const f = loadFiglet();
+  if (!f) return [];
+  if (_figletFonts === undefined) {
+    try {
+      _figletFonts = f.fontsSync();
+    } catch {
+      _figletFonts = [];
+    }
+  }
+  return _figletFonts.slice();
+}
+
+function generateFiglet(text, font) {
+  const f = loadFiglet();
+  if (!f) {
+    throw new AsciiArtFigletError('figlet is not available');
+  }
+  try {
+    return f.textSync(String(text ?? ''), { font });
+  } catch (err) {
+    throw new AsciiArtFigletError(`figlet render failed for font "${font}": ${err.message}`, err);
+  }
+}
+
+// Test-only cache reset; not used at runtime.
+function _resetCache() {
+  _figlet = undefined;
+  _figletFonts = undefined;
+}
+
+module.exports = {
+  AsciiArtFigletError,
+  loadFiglet,
+  listFigletFonts,
+  generateFiglet,
+  _resetCache,
+};