Detect local audio URLs in MediaUrlResolver

Recognizes mp3/wav/ogg/m4a and emits <audio controls class="kb-audio">.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/Markdown/MediaUrlResolver.php

@@ -6,12 +6,15 @@ class MediaUrlResolver
 {
     private const VIDEO_EXT = ['mp4', 'webm', 'ogv', 'mov', 'm4v'];
 
+    private const AUDIO_EXT = ['mp3', 'wav', 'ogg', 'm4a'];
+
     public function resolve(string $url): ?string
     {
         if ($url === '') {
             return null;
         }
-        return $this->detectVideo($url);
+        return $this->detectVideo($url)
+            ?? $this->detectAudio($url);
     }
 
     private function detectVideo(string $url): ?string
@@ -23,6 +26,15 @@ private function detectVideo(string $url): ?string
         return "<video src=\"{$safe}\" controls class=\"kb-video\"></video>";
     }
 
+    private function detectAudio(string $url): ?string
+    {
+        if (!in_array($this->getPathExtension($url), self::AUDIO_EXT, true)) {
+            return null;
+        }
+        $safe = htmlspecialchars($url, ENT_QUOTES, 'UTF-8');
+        return "<audio src=\"{$safe}\" controls class=\"kb-audio\"></audio>";
+    }
+
     private function getPathExtension(string $url): string
     {
         $path = parse_url($url, PHP_URL_PATH);

src/tests/Unit/Markdown/MediaUrlResolverTest.php

@@ -67,4 +67,24 @@ public function test_video_url_is_html_escaped(): void
         $this->assertStringNotContainsString('"quote.mp4"', $html);
         $this->assertStringContainsString('"', $html);
     }
+
+    #[DataProvider('audioUrls')]
+    public function test_audio_urls_produce_audio_tag(string $url): void
+    {
+        $html = $this->resolver->resolve($url);
+        $this->assertNotNull($html);
+        $this->assertStringStartsWith('<audio', $html);
+        $this->assertStringContainsString('controls', $html);
+        $this->assertStringContainsString('class="kb-audio"', $html);
+    }
+
+    public static function audioUrls(): array
+    {
+        return [
+            'mp3' => ['/clip.mp3'],
+            'wav' => ['/clip.wav'],
+            'ogg' => ['/clip.ogg'],
+            'm4a' => ['/clip.m4a'],
+        ];
+    }
 }