feat(camera): InputAction + DebugVM surface for retail chase camera

Four new InputAction entries for held-key offset integration
(CameraZoomIn/Out, CameraRaise/Lower; default unbound). Six new
DebugVM mirror properties forwarding to CameraDiagnostics so the
upcoming "Chase camera" DebugPanel section can drive them live.

Also folds in four small cleanups from the Task 4 code review:
- Both CameraDiagnostics-mutating tests in CameraControllerTests now
  use try/finally save/restore (consistency with Task-3 follow-up B)
- Drop unused `using System.Numerics` from CameraControllerTests
- Reword the XML doc on CameraController.Active to explain WHY both
  cameras are held simultaneously (flag flip takes effect on the
  next Active access without re-entry) rather than restating the
  getter logic

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

src/AcDream.App/Rendering/CameraController.cs

@@ -11,11 +11,11 @@ public sealed class CameraController
     public RetailChaseCamera? RetailChase { get; private set; }
 
     /// <summary>
-    /// The renderer-facing active camera. In chase mode, returns
+    /// The renderer-facing active camera. Both the legacy and retail
-    /// <see cref="RetailChase"/> when
+    /// chase cameras are held simultaneously so that flipping
-    /// <see cref="CameraDiagnostics.UseRetailChaseCamera"/> is true,
+    /// <see cref="CameraDiagnostics.UseRetailChaseCamera"/> takes effect
-    /// otherwise <see cref="Chase"/>. In fly mode returns
+    /// on the very next access to this property — no re-entry required,
-    /// <see cref="Fly"/>; default is <see cref="Orbit"/>.
+    /// no notification mechanism, no stale state.
     /// </summary>
     public ICamera Active
     {
@@ -53,9 +53,8 @@ public sealed class CameraController
     }
 
     /// <summary>
-    /// Enter chase mode with both candidate cameras. Both are held;
+    /// Store both cameras simultaneously; <see cref="Active"/> picks
-    /// <see cref="Active"/> picks based on
+    /// between them per-read via the flag — no re-entry needed on flip.
-    /// <see cref="CameraDiagnostics.UseRetailChaseCamera"/>.
     /// </summary>
     public void EnterChaseMode(ChaseCamera legacy, RetailChaseCamera retail)
     {

src/AcDream.UI.Abstractions/Input/InputAction.cs

@@ -262,4 +262,14 @@ public enum InputAction
     /// <summary>Fly-camera descend (Ctrl) — only meaningful while fly camera
     /// is active. K.1b binds it to ControlLeft; K.1c may rebind.</summary>
     AcdreamFlyDown,
+
+    // ── AcdreamCameraCommands ─────────────────────────────
+    /// <summary>Camera zoom in (held key, integrates Distance−= adjSpeed·dt). Default unbound.</summary>
+    CameraZoomIn,
+    /// <summary>Camera zoom out (held key, integrates Distance+= adjSpeed·dt). Default unbound.</summary>
+    CameraZoomOut,
+    /// <summary>Camera raise (held key, integrates Pitch+= adjSpeed·dt·0.02). Default unbound.</summary>
+    CameraRaise,
+    /// <summary>Camera lower (held key, integrates Pitch−= adjSpeed·dt·0.02). Default unbound.</summary>
+    CameraLower,
 }

src/AcDream.UI.Abstractions/Panels/Debug/DebugVM.cs

@@ -1,6 +1,7 @@
 using System.Numerics;
 using AcDream.Core.Combat;
 using AcDream.Core.Physics;
+using AcDream.Core.Rendering;
 
 namespace AcDream.UI.Abstractions.Panels.Debug;
 
@@ -290,6 +291,50 @@ public sealed class DebugVM
         set => PhysicsDiagnostics.ProbeAutoWalkEnabled = value;
     }
 
+    // ── Chase camera tunables (forward to CameraDiagnostics) ──────────
+
+    /// <summary>Runtime mirror of <see cref="CameraDiagnostics.UseRetailChaseCamera"/>.</summary>
+    public bool UseRetailChaseCamera
+    {
+        get => CameraDiagnostics.UseRetailChaseCamera;
+        set => CameraDiagnostics.UseRetailChaseCamera = value;
+    }
+
+    /// <summary>Runtime mirror of <see cref="CameraDiagnostics.AlignToSlope"/>.</summary>
+    public bool CameraAlignToSlope
+    {
+        get => CameraDiagnostics.AlignToSlope;
+        set => CameraDiagnostics.AlignToSlope = value;
+    }
+
+    /// <summary>Runtime mirror of <see cref="CameraDiagnostics.TranslationStiffness"/>.</summary>
+    public float CameraTranslationStiffness
+    {
+        get => CameraDiagnostics.TranslationStiffness;
+        set => CameraDiagnostics.TranslationStiffness = value;
+    }
+
+    /// <summary>Runtime mirror of <see cref="CameraDiagnostics.RotationStiffness"/>.</summary>
+    public float CameraRotationStiffness
+    {
+        get => CameraDiagnostics.RotationStiffness;
+        set => CameraDiagnostics.RotationStiffness = value;
+    }
+
+    /// <summary>Runtime mirror of <see cref="CameraDiagnostics.MouseLowPassWindowSec"/>.</summary>
+    public float CameraMouseLowPassWindowSec
+    {
+        get => CameraDiagnostics.MouseLowPassWindowSec;
+        set => CameraDiagnostics.MouseLowPassWindowSec = value;
+    }
+
+    /// <summary>Runtime mirror of <see cref="CameraDiagnostics.CameraAdjustmentSpeed"/>.</summary>
+    public float CameraAdjustmentSpeed
+    {
+        get => CameraDiagnostics.CameraAdjustmentSpeed;
+        set => CameraDiagnostics.CameraAdjustmentSpeed = value;
+    }
+
     // ── Action hooks invoked by panel buttons ──────────────────────────
 
     /// <summary>

tests/AcDream.App.Tests/Rendering/CameraControllerTests.cs

@@ -1,4 +1,3 @@
-using System.Numerics;
 using AcDream.App.Rendering;
 using AcDream.Core.Rendering;
 using Xunit;
@@ -21,47 +20,76 @@ public class CameraControllerTests
     [Fact]
     public void ChaseMode_WhenFlagOff_ActiveIsLegacy()
     {
-        CameraDiagnostics.UseRetailChaseCamera = false;
+        bool saved = CameraDiagnostics.UseRetailChaseCamera;
-        var (ctl, legacy, _) = MakeChaseFixture();
+        try
-        Assert.Same(legacy, ctl.Active);
+        {
-        Assert.True(ctl.IsChaseMode);
+            CameraDiagnostics.UseRetailChaseCamera = false;
+            var (ctl, legacy, _) = MakeChaseFixture();
+            Assert.Same(legacy, ctl.Active);
+            Assert.True(ctl.IsChaseMode);
+        }
+        finally
+        {
+            CameraDiagnostics.UseRetailChaseCamera = saved;
+        }
     }
 
     [Fact]
     public void ChaseMode_WhenFlagOn_ActiveIsRetail()
     {
-        CameraDiagnostics.UseRetailChaseCamera = true;
+        bool saved = CameraDiagnostics.UseRetailChaseCamera;
-        var (ctl, _, retail) = MakeChaseFixture();
+        try
-        Assert.Same(retail, ctl.Active);
+        {
-        Assert.True(ctl.IsChaseMode);
+            CameraDiagnostics.UseRetailChaseCamera = true;
-
+            var (ctl, _, retail) = MakeChaseFixture();
-        // Reset.
+            Assert.Same(retail, ctl.Active);
-        CameraDiagnostics.UseRetailChaseCamera = false;
+            Assert.True(ctl.IsChaseMode);
+        }
+        finally
+        {
+            CameraDiagnostics.UseRetailChaseCamera = saved;
+        }
     }
 
     [Fact]
     public void ChaseMode_FlagFlipped_ActiveSwaps()
     {
-        CameraDiagnostics.UseRetailChaseCamera = false;
+        bool saved = CameraDiagnostics.UseRetailChaseCamera;
-        var (ctl, legacy, retail) = MakeChaseFixture();
+        try
-        Assert.Same(legacy, ctl.Active);
+        {
+            CameraDiagnostics.UseRetailChaseCamera = false;
+            var (ctl, legacy, retail) = MakeChaseFixture();
+            Assert.Same(legacy, ctl.Active);
 
-        CameraDiagnostics.UseRetailChaseCamera = true;
+            CameraDiagnostics.UseRetailChaseCamera = true;
-        Assert.Same(retail, ctl.Active);
+            Assert.Same(retail, ctl.Active);
 
-        CameraDiagnostics.UseRetailChaseCamera = false;
+            CameraDiagnostics.UseRetailChaseCamera = false;
-        Assert.Same(legacy, ctl.Active);
+            Assert.Same(legacy, ctl.Active);
+        }
+        finally
+        {
+            CameraDiagnostics.UseRetailChaseCamera = saved;
+        }
     }
 
     [Fact]
     public void ExitChaseMode_ClearsBothCameras()
     {
-        CameraDiagnostics.UseRetailChaseCamera = false;
+        bool saved = CameraDiagnostics.UseRetailChaseCamera;
-        var (ctl, _, _) = MakeChaseFixture();
+        try
-        ctl.ExitChaseMode();
+        {
+            CameraDiagnostics.UseRetailChaseCamera = false;
+            var (ctl, _, _) = MakeChaseFixture();
+            ctl.ExitChaseMode();
 
-        Assert.Null(ctl.Chase);
+            Assert.Null(ctl.Chase);
-        Assert.Null(ctl.RetailChase);
+            Assert.Null(ctl.RetailChase);
-        Assert.False(ctl.IsChaseMode);
+            Assert.False(ctl.IsChaseMode);
+        }
+        finally
+        {
+            CameraDiagnostics.UseRetailChaseCamera = saved;
+        }
     }
 }