Detect local video URLs in MediaUrlResolver

Recognizes mp4/webm/ogv/mov/m4v on URL path (case-insensitive, ignoring
query strings) and emits <video controls class="kb-video">.

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

src/app/Markdown/MediaUrlResolver.php

@@ -4,11 +4,31 @@
 
 class MediaUrlResolver
 {
+    private const VIDEO_EXT = ['mp4', 'webm', 'ogv', 'mov', 'm4v'];
+
     public function resolve(string $url): ?string
     {
         if ($url === '') {
             return null;
         }
-        return null;
+        return $this->detectVideo($url);
+    }
+
+    private function detectVideo(string $url): ?string
+    {
+        if (!in_array($this->getPathExtension($url), self::VIDEO_EXT, true)) {
+            return null;
+        }
+        $safe = htmlspecialchars($url, ENT_QUOTES, 'UTF-8');
+        return "<video src=\"{$safe}\" controls class=\"kb-video\"></video>";
+    }
+
+    private function getPathExtension(string $url): string
+    {
+        $path = parse_url($url, PHP_URL_PATH);
+        if ($path === null || $path === false) {
+            return '';
+        }
+        return strtolower(pathinfo($path, PATHINFO_EXTENSION));
     }
 }

src/tests/Unit/Markdown/MediaUrlResolverTest.php

@@ -35,4 +35,36 @@ public static function nonMediaUrls(): array
             'youtu.be lookalike host' => ['https://example.com/youtu.be-fake/abc'],
         ];
     }
+
+    #[DataProvider('videoUrls')]
+    public function test_video_urls_produce_video_tag(string $url): void
+    {
+        $html = $this->resolver->resolve($url);
+        $this->assertNotNull($html);
+        $this->assertStringStartsWith('<video', $html);
+        $this->assertStringContainsString('controls', $html);
+        $this->assertStringContainsString('class="kb-video"', $html);
+    }
+
+    public static function videoUrls(): array
+    {
+        return [
+            'mp4' => ['/demo.mp4'],
+            'webm' => ['/demo.webm'],
+            'ogv' => ['/demo.ogv'],
+            'mov' => ['/demo.mov'],
+            'm4v' => ['/demo.m4v'],
+            'uppercase extension' => ['/demo.MP4'],
+            'with query string' => ['https://example.com/path/demo.mp4?token=abc'],
+            'absolute http' => ['https://example.com/demo.mp4'],
+        ];
+    }
+
+    public function test_video_url_is_html_escaped(): void
+    {
+        $html = $this->resolver->resolve('/path/with"quote.mp4');
+        $this->assertNotNull($html);
+        $this->assertStringNotContainsString('"quote.mp4"', $html);
+        $this->assertStringContainsString('&quot;', $html);
+    }
 }