Add lazy piano transcription and optional leased server worker

tests/piano-engine.spec.js

@@ -0,0 +1,56 @@
+const { test, expect } = require('@playwright/test');
+const { openClassic } = require('./helpers/classic-fixture');
+test('Basic Pitch is lazy and transcribes a short synthetic WAV', async ({ page }) => {
+  test.setTimeout(120000);
+  page.on('requestfailed', (req) =>
+    console.log('Engine request failed:', req.url(), req.failure()?.errorText),
+  );
+  const requests = [];
+  page.on('request', (req) => {
+    if (/esm\.sh|jsdelivr.*basic-pitch/.test(req.url())) requests.push(req.url());
+  });
+  await openClassic(page);
+  expect(requests).toEqual([]);
+  const result = await page.evaluate(async () => {
+    const rate = 22050,
+      samples = rate * 2,
+      buffer = new ArrayBuffer(44 + samples * 2),
+      view = new DataView(buffer);
+    const text = (offset, value) => {
+      [...value].forEach((c, i) => view.setUint8(offset + i, c.charCodeAt(0)));
+    };
+    text(0, 'RIFF');
+    view.setUint32(4, 36 + samples * 2, true);
+    text(8, 'WAVE');
+    text(12, 'fmt ');
+    view.setUint32(16, 16, true);
+    view.setUint16(20, 1, true);
+    view.setUint16(22, 1, true);
+    view.setUint32(24, rate, true);
+    view.setUint32(28, rate * 2, true);
+    view.setUint16(32, 2, true);
+    view.setUint16(34, 16, true);
+    text(36, 'data');
+    view.setUint32(40, samples * 2, true);
+    for (let i = 0; i < samples; i++)
+      view.setInt16(44 + i * 2, Math.sin((2 * Math.PI * 440 * i) / rate) * 16000, true);
+    const engine = await import('/piano-engine.mjs');
+    const result = await engine.transcribe(buffer.slice(0), () => {});
+    const tf = await import('https://esm.sh/@tensorflow/tfjs@4.22.0');
+    const before = tf.memory().numTensors;
+    const second = await engine.transcribe(buffer.slice(0), () => {});
+    return {
+      engine: result.engine,
+      notes: PianoCore.fromBasicPitch(result.notes),
+      secondNotes: second.notes.length,
+      before,
+      after: tf.memory().numTensors,
+    };
+  });
+  expect(result.engine).toMatch(/basic-pitch-1.0.1\/(webgpu|webgl|cpu)/);
+  expect(requests.length).toBeGreaterThan(0);
+  expect(result.notes.length).toBeGreaterThan(0);
+  expect(result.notes.some((n) => n.pitch === 69)).toBe(true);
+  expect(result.secondNotes).toBeGreaterThan(0);
+  expect(result.after).toBe(result.before);
+});