Update pad parser to handle fractional pitch and trim length correctly

tests/pad-parser.test.ts

@@ -0,0 +1,44 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { collectPads } from '../src/lib/parsers';
+import { TarFile } from '../src/lib/untar';
+
+function padFile(name: string, length: 26 | 27) {
+  const data = new Uint8Array(length);
+  return { data, file: new TarFile(name, data.length, data) };
+}
+
+test('decodes optional fractional pitch arithmetically for 26- and 27-byte pad records', () => {
+  const native = padFile('pads/a/p01', 26);
+  native.data[17] = 0xff;
+  const extended = padFile('pads/a/p02', 27);
+  extended.data[17] = 0xff;
+  extended.data[26] = 91;
+
+  const pads = collectPads([native.file, extended.file], []);
+
+  assert.equal(pads.a[0].pitch, -1);
+  assert.ok(Math.abs(pads.a[1].pitch - -0.09) < 1e-12);
+});
+
+test('reads trim length as unsigned 32-bit little-endian data', () => {
+  const pad = padFile('pads/a/p01', 26);
+  pad.data.set([0x03, 0x02, 0x01], 4);
+  pad.data.set([0x04, 0x03, 0x02, 0x01], 8);
+
+  const parsed = collectPads([pad.file], []).a[0];
+
+  assert.equal(parsed.trimLeft, 0x010203);
+  assert.equal(parsed.trimRight, 0x010203 + 0x01020304);
+});
+
+test('treats every nonzero mute byte as shared mute-group membership', () => {
+  const member = padFile('pads/a/p01', 26);
+  const nonmember = padFile('pads/a/p02', 26);
+  member.data[22] = 200;
+
+  const pads = collectPads([member.file, nonmember.file], []).a;
+
+  assert.equal(pads[0].inChokeGroup, true);
+  assert.equal(pads[1].inChokeGroup, false);
+});