JR-004, JR-005, JR-006: scene-scoped read path

Presence was decided by a LINQ predicate inline in the controller, so the
semantics SR-002 sets were nowhere stated in code -- the read path complied by
accident rather than by requirement. PresenceLookup is now the unit that
decides, tagged, with the reasoning next to it.

JR-004: windows are served exactly as given. UT-021 pins that [0,10] and
[10,20] are not merged despite looking mergeable -- two windows mean a genuine
departure and return, and collapsing them answers a different question from the
one the truth file asked. UT-022 pins a byte-identical round trip.

JR-005: bounds inclusive at both ends, zero-length windows are real sightings
rather than degenerate ones to discard, overlaps resolve.

The wording was the larger half of JR-005. The overlay rendered a bare list: it
asserted nothing, but told the viewer nothing either, and the default reading of
a paused frame is "these people are on screen" -- exactly what SR-002 forbids.
It now carries an "In this scene" heading. ActorAtTime became ActorInScene, and
README no longer contains "on screen" anywhere; it stated the forbidden reading
outright in seven places, including the opening sentence.

JR-006: measured rather than assumed. UT-023 builds 50 actors x 1000 windows and
asserts the response is bounded by actor count, never window count. The lookup
is a full scan on purpose -- an early exit on `start > t` would exploit the
sortedness the format requires, but would silently under-report the moment one
producer emitted windows out of order. UT-020 pins that unsorted input still
resolves; WindowsAreSorted is a diagnostic, not a correctness dependency.

Third mutation check: making the end bound exclusive fails UT-016 and UT-018 and
nothing else. One character turns an inclusive window into a half-open one,
dropping an actor at exactly the moment a scene ends.

TRACES: UT-016, UT-017, UT-018, UT-019, UT-020, UT-021, UT-022, UT-023
TRACES: JR-004, JR-005, JR-006 | SR-002

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Jellyfin.Plugin.JRay/Controllers/ActorsController.cs

@@ -1,8 +1,8 @@
 using System;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Jellyfin.Plugin.JRay.Models;
+using Jellyfin.Plugin.JRay.Services;
 using Jellyfin.Plugin.JRay.Services.Interfaces;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Http;
@@ -38,7 +38,7 @@ public class ActorsController : ControllerBase
     }
 
     /// <summary>
-    /// Gets the full actor timeline (every actor with their on-screen scene windows) for a movie.
+    /// Gets the full actor timeline (every actor with their scene-presence windows) for a movie.
     /// </summary>
     /// <param name="itemId">The Jellyfin item id.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
@@ -58,7 +58,7 @@ public class ActorsController : ControllerBase
     }
 
     /// <summary>
-    /// Gets the JRay context (currently: on-screen actors) at a given timestamp.
+    /// Gets the JRay context (currently: the actors in the scene) at a given timestamp.
     /// This is an extensible envelope — future fields (locations, trivia, etc.)
     /// will be added here without changing the route.
     /// </summary>
@@ -78,9 +78,9 @@ public class ActorsController : ControllerBase
         }
 
         var context = new JRayContext();
-        foreach (var actor in truth.Actors.Where(actor => actor.Scenes.Any(scene => scene.Length == 2 && scene[0] <= t && t <= scene[1])))
+        foreach (var actor in PresenceLookup.ActorsPresentAt(truth, t))
         {
-            context.Actors.Add(new ActorAtTime
+            context.Actors.Add(new ActorInScene
             {
                 Name = actor.Name,
                 ImdbId = actor.ImdbId,