feat: add IIntroProvider for Wholphin/cinema-mode compatibility

Registers TrailerIntroProvider as IIntroProvider. Queries fake-movie
items in the output folder and returns their local trailer extras
(LocalTrailers) as IntroInfo — mirroring jellyfin-plugin-cinemamode's
proven pattern so Wholphin plays the actual trailer, not the 3-second
black placeholder.

Recursion guard: items whose path starts with the output folder are
excluded from intro injection, so Wholphin's getIntros call on the
intro item itself returns empty. Server-scoped query bypasses library
visibility restrictions so hidden trailer libraries still work.

Adds TrailersPerMovie config option (default 1, 0 = disabled).

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

Jellyfin.Plugin.CinemaTrailers4Jellyfins/Configuration/PluginConfiguration.cs

@@ -38,5 +38,10 @@ namespace Jellyfin.Plugin.CinemaTrailers4Jellyfins.Configuration
 
         /// <summary>Maximum trailers to keep on disk. Oldest are deleted first when exceeded. 0 = unlimited.</summary>
         public int MaxTotalTrailers { get; set; } = 50;
+
+        // ── IIntroProvider (Cinema Mode / Wholphin) ───────────────────────────
+
+        /// <summary>Number of trailers to inject before each movie via IIntroProvider. 0 = disabled.</summary>
+        public int TrailersPerMovie { get; set; } = 1;
     }
 }

Jellyfin.Plugin.CinemaTrailers4Jellyfins/Configuration/config.html

@@ -217,6 +217,26 @@
                         </div>
                     </fieldset>
 
+                    <!-- Cinema Mode Integration -->
+                    <fieldset class="verticalSection verticalSection-extrabottompadding">
+                        <legend><h3 class="sectionTitle">Cinema Mode Integration</h3></legend>
+                        <p class="fieldDescription">
+                            When enabled, this plugin registers as an <strong>IIntroProvider</strong> and
+                            injects downloaded trailers before movies — compatible with Jellyfin's built-in
+                            cinema mode support and clients like Wholphin.
+                            The output folder must be added as a Jellyfin <strong>Movies</strong> library
+                            and scanned before trailers appear.
+                        </p>
+                        <div class="inputContainer">
+                            <label class="inputLabel inputLabelUnfocused" for="trailers-per-movie">Trailers per movie</label>
+                            <input type="number" id="trailers-per-movie" is="emby-input" min="0" max="10" />
+                            <div class="fieldDescription">
+                                Number of trailers to play before each movie. Set to 0 to disable.
+                                Default: 1.
+                            </div>
+                        </div>
+                    </fieldset>
+
                     <!-- Advanced -->
                     <fieldset class="verticalSection verticalSection-extrabottompadding">
                         <legend><h3 class="sectionTitle">Advanced</h3></legend>
@@ -264,6 +284,7 @@
                             document.getElementById('lang-' + code).checked = langs.length === 0 || langs.indexOf(code) !== -1;
                         });
                     document.getElementById('max-total-trailers').value     = config.MaxTotalTrailers ?? 50;
+                    document.getElementById('trailers-per-movie').value     = config.TrailersPerMovie ?? 1;
                     Dashboard.hideLoadingMsg();
                 });
             });
@@ -291,6 +312,7 @@
                     // If all are checked treat it as "no preference" (empty string)
                     config.AllowedLanguages       = checkedLangs.length === allLangCodes.length ? '' : checkedLangs.join(',');
                     config.MaxTotalTrailers       = parseInt(document.getElementById('max-total-trailers').value, 10) || 50;
+                    config.TrailersPerMovie       = parseInt(document.getElementById('trailers-per-movie').value, 10) || 0;
                     ApiClient.updatePluginConfiguration(pluginId, config)
                         .then(Dashboard.processPluginConfigurationUpdateResult);
                 });