fix #389 review round: settings v3 FOV migration + live apply; AD-90

Dual-lens Opus review of 7e0c1303 (reports committed under
docs/research/). The law, gate, and vertical application are CONFIRMED
at instruction-byte level against the PDB-paired acclient.exe (the BN
text FPU-elides this whole area); the fix round addresses the findings:

- Blast MUST-FIX 1: real schema migration instead of a hand-edited dev
  file. SettingsStore v2->v3: a pre-v3 display.fieldOfView was the
  applied vertical FOV in degrees; v3 means retail's m_fGameFOV.
  LoadDisplay migrates on read - the untouched old default 60 maps to
  the retail default 90; a deliberate other value preserves its visible
  16:9 framing (x (16/9 - 0.1)), clamped to the registered [10,160];
  the next save stamps v3 and migration never reruns. The dev
  settings.json hand-edit was reverted so the migration owns it.
- Blast MUST-FIX 2 / mechanism M2: the Field of View now applies LIVE on
  Save (retail: Render::GRPCallback_OnRenderPreferenceChanged @0x0054d999
  -> SmartBox::SetDefaultFov). RuntimeSettingsTargets gains the camera
  graph and applies through ApplyDisplayWindowState - the update-phase
  seam, deliberately NOT the render-phase preview path (the review's
  WATCH-3 cull-vs-raster landmine).
- Mechanism M1 -> register row AD-90: retail's divisor aspect runs
  through the Render.AspectRatio preference (ComputeAspectForViewport
  @0x0054f150, (w/h) x pref x 0.75) - exactly raw w/h at the registered
  default, which is what acdream assumes; retail's NaN-through-the-gate
  quirk (M3) is folded into the same row as deliberately not reproduced.
- Docs: RetailFieldOfView now cites the decisive vertical proof
  (D3DXMatrixPerspectiveFovLH fovy slot @0x0059ab71), the unconditional
  SmartBox::RenderNormalMode site, and M4's exact horizontal numbers
  (89.0/83.9/80.6 deg); the Config FOV row comment updated to LIVE.
- Blast WATCH 4 disposition: the 15 replay-harness PI/3 constants stay -
  they are CAPTURE-TIME camera parameters for recorded fixtures, not
  production framing; changing them would invalidate the replays.

Tests: +6 SettingsStore migration facts, +1 live-apply fact.
App suite 4,962/3 skips; UI.Abstractions 922.

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

src/AcDream.App/Settings/RuntimeSettingsTargets.cs

@@ -286,6 +286,7 @@ internal sealed class RuntimeSettingsTargets : IRuntimeSettingsTargets
     private readonly ICommandBus _commands;
     private readonly Action<string> _log;
     private readonly OpenAlAudioEngine? _audio;
+    private readonly CameraController? _cameras;
 
     public RuntimeSettingsTargets(
         IRuntimeDisplayWindowTarget displayWindow,
@@ -301,7 +302,14 @@ internal sealed class RuntimeSettingsTargets : IRuntimeSettingsTargets
         // ApplyAudio's doc. Optional/trailing so every pre-existing
         // construction site keeps compiling unchanged (matches
         // chatOpacity/log's own optional-trailing shape).
-        OpenAlAudioEngine? audio = null)
+        OpenAlAudioEngine? audio = null,
+        // #389 blast-review MUST-FIX 2: retail's FOV preference applies LIVE
+        // (Render::GRPCallback_OnRenderPreferenceChanged @0x0054d999 →
+        // SmartBox::SetDefaultFov → m_fGameFOV, re-read by the smartbox
+        // sites every render) — the saved Field of View must reach the
+        // cameras on Save, not on the next launch. Null on hosts with no
+        // camera graph (headless / fixture callers).
+        CameraController? cameras = null)
         : this(
             displayWindow,
             new RuntimeQualityApplicationTarget(
@@ -317,7 +325,8 @@ internal sealed class RuntimeSettingsTargets : IRuntimeSettingsTargets
             chatOpacity is null
                 ? NullRuntimeChatOpacityTarget.Instance
                 : new RuntimeChatOpacityTarget(chatOpacity),
-            audio)
+            audio,
+            cameras)
     {
     }
 
@@ -328,7 +337,8 @@ internal sealed class RuntimeSettingsTargets : IRuntimeSettingsTargets
         ICommandBus commands,
         Action<string>? log = null,
         IRuntimeChatOpacityTarget? chatOpacity = null,
-        OpenAlAudioEngine? audio = null)
+        OpenAlAudioEngine? audio = null,
+        CameraController? cameras = null)
     {
         _displayWindow = displayWindow
             ?? throw new ArgumentNullException(nameof(displayWindow));
@@ -338,10 +348,20 @@ internal sealed class RuntimeSettingsTargets : IRuntimeSettingsTargets
         _commands = commands ?? throw new ArgumentNullException(nameof(commands));
         _log = log ?? Console.WriteLine;
         _audio = audio;
+        _cameras = cameras;
     }
 
-    public void ApplyDisplayWindowState(DisplaySettings display) =>
+    public void ApplyDisplayWindowState(DisplaySettings display)
+    {
         _displayWindow.Apply(display);
+        // #389 blast MUST-FIX 2 (see the ctor's cameras doc): the Field of
+        // View applies live on Save, from the update-phase save handler —
+        // deliberately NOT from the render-phase preview seam
+        // (WorldRenderFrameBuilder.Apply), whose mid-frame camera mutation
+        // is the review's WATCH-3 cull-vs-raster landmine.
+        if (_cameras is not null)
+            RuntimeSettingsStartupTargets.ApplyFieldOfView(_cameras, display.FieldOfView);
+    }
 
     /// <summary>Campaign OP slice OP6: reuses the SAME static helper the
     /// startup path (<see cref="RuntimeSettingsStartupTargets.ApplyAudio"/>)