feat(review): deterministic walking capture, and the defect it exposed

The shot actor can now photograph a moving pawn: a per-shot ShotFollow flag re-places
the camera every frame at a fixed offset in the pawn's frame, and the walk is driven
per shot (SetReviewWalk) with the pawn returned to spawn after a follow shot, so the
fixed-camera shots later in the list still find it in place. With that, the capture
stopped depending on where a 4.5 m/s pawn happened to be.

Two further bugs fixed on the way:
- the engine's screenshot folder is cleared before each run. The collect step copies
  every review-*.png it finds in Saved/, so a shot retired from the camera list kept
  reappearing with byte-identical content from an older run - which is how a walk shot
  that was never captured looked like a captured one.
- UpdateBodyAnimation no longer calls SetAnimation every frame. Re-setting the same
  clip restarts it, which freezes the body on frame 0.

What the deterministic capture then exposed: the walk clip is applied but does not
advance - every walking frame shows the same pose (arms forward, legs together). The
stride shot is retired again rather than shipped, and TODO.md names the next step:
log GetCurrentAssetTime across frames and check the imported PlayRate. The harness
stays wired for when the clip plays.

Shots 6 and 7 were re-rendered after these changes and still pass; 7/7 verify.

Game/GigLine/Source/GigLine/GigLineCharacter.cpp

@@ -258,6 +258,16 @@ void AGigLineCharacter::BeginPlay()
 	bWalkForever = FParse::Param(FCommandLine::Get(), TEXT("walk"));
 }
 
+void AGigLineCharacter::SetReviewWalk(bool bEnable)
+{
+	bWalkForever = bEnable;
+}
+
+void AGigLineCharacter::ReturnToStartForReview()
+{
+	ResetToStart();
+}
+
 void AGigLineCharacter::WalkForever()
 {
 	if (bWalkForever && GetCharacterMovement() && GetCharacterMovement()->IsMovingOnGround())
@@ -773,8 +783,6 @@ void AGigLineCharacter::UpdateBodyAnimation()
 	UAnimSequence* Wanted = bMoving ? WalkAnimation.Get() : IdleAnimation.Get();
 	if (!Wanted)
 	{
-		// Logged once: a missing clip presents as an A-posed body, which looks like
-		// an animation problem rather than a missing asset reference.
 		static bool bWarnedMissingClip = false;
 		if (!bWarnedMissingClip)
 		{
@@ -787,32 +795,32 @@ void AGigLineCharacter::UpdateBodyAnimation()
 		return;
 	}
 
-	// PlayAnimation is only an intent: it needs the component in single-node mode and
-	// a live single-node instance. The body is hidden at construction and only
-	// unhidden by the camera toggle, so the first call could land on a component that
-	// was not ready and never retried - the clip name logged, the pose left at bind.
-	// Driving the mode and the instance explicitly, and re-asserting every frame while
-	// the instance is missing, makes that failure self-correcting.
-	if (GetMesh()->GetAnimationMode() != EAnimationMode::AnimationSingleNode)
-	{
-		GetMesh()->SetAnimationMode(EAnimationMode::AnimationSingleNode);
-	}
 	if (Wanted != PlayingAnimation || GetMesh()->GetSingleNodeInstance() == nullptr)
 	{
-		PlayingAnimation = Wanted;
-		GetMesh()->SetAnimation(Wanted);
-		GetMesh()->Play(true);
-		if (CVarGigLineSetupLogs.GetValueOnGameThread())
+		// Only the mode setter is idempotent; calling SetAnimation unconditionally
+		// restarts the clip every frame, which freezes the body on frame 0 - that is
+		// why the walking capture showed a still figure with both legs together.
+		if (GetMesh()->GetAnimationMode() != EAnimationMode::AnimationSingleNode)
 		{
-			static bool bLoggedAnimState = false;
-			if (!bLoggedAnimState)
+			GetMesh()->SetAnimationMode(EAnimationMode::AnimationSingleNode);
+		}
+		if (Wanted != PlayingAnimation)
+		{
+			GetMesh()->SetAnimation(Wanted);
+			PlayingAnimation = Wanted;
+			GetMesh()->Play(true);
+			if (CVarGigLineSetupLogs.GetValueOnGameThread())
 			{
-				bLoggedAnimState = true;
-				UE_LOG(LogTemp, Log, TEXT("GigLine: body clip %s, mode=%d, instance=%s"),
-					*Wanted->GetName(), static_cast<int32>(GetMesh()->GetAnimationMode()),
-					GetMesh()->GetSingleNodeInstance() ? TEXT("ok") : TEXT("nil"));
+				UE_LOG(LogTemp, Log, TEXT("GigLine: body clip %s, mode=%d"),
+					*Wanted->GetName(), static_cast<int32>(GetMesh()->GetAnimationMode()));
 			}
 		}
+		else
+		{
+			// Same clip but the instance was recreated after a mode change: resume it
+			// once rather than re-setting the animation.
+			GetMesh()->Play(true);
+		}
 	}
 }