docs: update AGENTS.md and README for new features, add JS tests

Docs:
- AGENTS.md: updated toolchain section with js-lint/js-test tasks,
  expanded web/ui/ directory listing, added event delegation and
  Web Audio API to key patterns, updated testing section
- README: marked issue #9 (Audio Preview Player) as done
- .gitignore: added akai-fetch.test and cover.out

Tests:
- Moved groupWavs and cleanName to util.js (pure functions)
- Added 10 new JS tests: 6 groupWavs, 4 cleanName
- Total JS tests: 29 (up from 19)

web/ui/util.test.js

@@ -1,6 +1,6 @@
 const { describe, it } = require('node:test')
 const assert = require('node:assert/strict')
-const { esc, sanitize, formatBytes, formatTime } = require('./util.js')
+const { esc, sanitize, formatBytes, formatTime, groupWavs, cleanName } = require('./util.js')
 
 describe('esc', () => {
   it('escapes HTML entities', () => {
@@ -88,4 +88,74 @@ describe('formatTime', () => {
   it('formats large times', () => {
     assert.strictEqual(formatTime(3661), '61:01')
   })
+})
+
+describe('groupWavs', () => {
+  it('groups by library and program', () => {
+    const paths = [
+      'LibA/Prog1/kick.wav',
+      'LibA/Prog1/snare.wav',
+      'LibA/Prog2/hat.wav'
+    ]
+    const result = groupWavs(paths)
+    assert.strictEqual(Object.keys(result).length, 1)
+    assert.strictEqual(Object.keys(result.LibA).length, 2)
+    assert.strictEqual(result.LibA.Prog1.length, 2)
+    assert.strictEqual(result.LibA.Prog2.length, 1)
+  })
+
+  it('handles multiple libraries', () => {
+    const paths = [
+      'LibA/kick.wav',
+      'LibB/snare.wav'
+    ]
+    const result = groupWavs(paths)
+    assert.strictEqual(Object.keys(result).length, 2)
+    assert.strictEqual(result.LibA.LibA[0].name, 'kick')
+    assert.strictEqual(result.LibB.LibB[0].name, 'snare')
+  })
+
+  it('strips .wav extension case-insensitively', () => {
+    const paths = ['Lib/Prog/KICK.WAV']
+    const result = groupWavs(paths)
+    assert.strictEqual(result.Lib.Prog[0].name, 'KICK')
+  })
+
+  it('handles deeply nested paths', () => {
+    const paths = ['A/B/C/D/file.wav']
+    const result = groupWavs(paths)
+    assert.strictEqual(result.A.B.length, 1)
+    assert.strictEqual(result.A.B[0].name, 'file')
+    assert.strictEqual(result.A.B[0].fullPath, 'A/B/C/D/file.wav')
+  })
+
+  it('handles flat paths with no directory', () => {
+    const paths = ['sound.wav']
+    const result = groupWavs(paths)
+    assert.strictEqual(Object.keys(result).length, 1)
+    assert.strictEqual(Object.keys(result['']).length, 1)
+  })
+
+  it('returns empty object for empty input', () => {
+    const result = groupWavs([])
+    assert.strictEqual(Object.keys(result).length, 0)
+  })
+})
+
+describe('cleanName', () => {
+  it('replaces underscores with spaces', () => {
+    assert.strictEqual(cleanName('hello_world'), 'hello world')
+  })
+
+  it('collapses multiple underscores', () => {
+    assert.strictEqual(cleanName('AMG_-_Black__II'), 'AMG - Black II')
+  })
+
+  it('trims leading/trailing spaces from underscores', () => {
+    assert.strictEqual(cleanName('_padded_'), 'padded')
+  })
+
+  it('preserves regular text', () => {
+    assert.strictEqual(cleanName('Kick Drum'), 'Kick Drum')
+  })
 })