[YouTube] Fix HTTP 403 on DASH fragments by adding android_vr client

- Add android_vr (Oculus Quest 3) as first-priority InnerTube client,
  replacing android_sdkless which is now blocked by YouTube's CDN
- Remove break on n parameter that prevented all formats from being added
- Set client User-Agent on format download headers to avoid CDN mismatch

Ref: yt-dlp/yt-dlp#15726

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

youtube_dl/extractor/youtube.py

@@ -90,6 +90,24 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
 
     # priority order for now
     _INNERTUBE_CLIENTS = o_dict((
+        # thx yt-dlp/yt-dlp#15726
+        ('android_vr', {
+            'INNERTUBE_CONTEXT': {
+                'client': {
+                    'clientName': 'ANDROID_VR',
+                    'clientVersion': '1.62.27',
+                    'deviceMake': 'Oculus',
+                    'deviceModel': 'Quest 3',
+                    'androidSdkVersion': 32,
+                    'userAgent': 'com.google.android.apps.youtube.vr.oculus/1.62.27 (Linux; U; Android 12L; eureka-user Build/SQ3A.220605.009.A1) gzip',
+                    'osName': 'Android',
+                    'osVersion': '12L',
+                },
+            },
+            'INNERTUBE_CONTEXT_CLIENT_NAME': 28,
+            'REQUIRE_JS_PLAYER': False,
+            'WITH_COOKIES': False,
+        }),
         # Doesn't require a PoToken for some reason: thx yt-dlp/yt-dlp#14693
         ('android_sdkless', {
             'INNERTUBE_CONTEXT': {
@@ -2364,6 +2382,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         is_live = traverse_obj(player_response, ('videoDetails', 'isLive'))
 
         fetched_timestamp = None
+        client_user_agent = None
         if False and not player_response:
             player_response = self._call_api(
                 'player', {'videoId': video_id}, video_id)
@@ -2455,6 +2474,10 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                         'streamingData', 'hlsManifestUrl', T(url_or_none))):
                     player_response['streamingData']['hlsManifestUrl'] = hls
 
+            # Save client User-Agent for use in format download headers
+            client_user_agent = traverse_obj(client, (
+                'INNERTUBE_CONTEXT', 'client', 'userAgent'))
+
         def is_agegated(playability):
             # playability: dict
             if not playability:
@@ -2654,10 +2677,6 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                     self.write_debug(error_to_compat_str(e), only_once=True)
                     continue
 
-            if parse_qs(fmt_url).get('n'):
-                # this and (we assume) all the formats here are n-scrambled
-                break
-
             language_preference = (
                 10 if audio_track.get('audioIsDefault')
                 else -10 if 'descriptive' in (traverse_obj(audio_track, ('displayName', T(lower))) or '')
@@ -2678,6 +2697,8 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 # Strictly de-prioritize 3gp formats
                 'preference': -2 if itag == '17' else None,
             }
+            if client_user_agent:
+                dct['http_headers'] = {'User-Agent': client_user_agent}
             if itag:
                 itags[itag].add(('https', dct.get('language')))
             self._unthrottle_format_urls(video_id, player_url, dct)