feat(camera): third-person rig, V toggle, visible body

One pawn, both rigs (ADR-9): a skeletal body hidden in first person, a
collision-tested spring arm, and a toggle that swaps the active camera and the
body's visibility. Shipped default stays first person; -thirdperson starts the
pawn in the third-person rig so the review shot is reproducible, and the
screenshot run passes it.

Three defects found and two fixed:
- The skin material had no SkeletalMesh usage flag, so Unreal silently substituted
  the default grey. That is why the body rendered as clay.
- render_screenshots.sh still called ./Engine/... on this branch (the fix lives on
  the facade branch and never reached main); applied here so the shots generate.
- OPEN: the idle clip is bound and PlayAnimation is called - the run logs the clip
  name - but the body still renders in bind pose, arms out. Recorded with that
  evidence in TODO.md rather than called done.

Shot 5 (demo-third-person) added and documented; camera collision is implemented
but unproven, since the spawn has open space behind it.

Game/GigLine/Source/GigLine/GigLineCharacter.h

@@ -7,9 +7,11 @@
 #include "InputActionValue.h"
 #include "GigLineCharacter.generated.h"
 
+class UAnimSequence;
 class UCameraComponent;
 class UInputAction;
 class UInputMappingContext;
+class USpringArmComponent;
 
 
 /**
@@ -29,6 +31,7 @@ public:
 
 	virtual void BeginPlay() override;
 	virtual void SetupPlayerInputComponent(class UInputComponent* PlayerInputComponent) override;
+	virtual void Tick(float DeltaSeconds) override;
 
 protected:
 	/** Loads the Enhanced Input assets from /Game/Input; called from BeginPlay. */
@@ -38,6 +41,23 @@ protected:
 	void ResetToStart();
 	void TogglePause();
 
+	/** Swaps between the first-person and third-person rigs (V). */
+	void ToggleCamera();
+
+	/**
+	 * Plays the idle or walk clip on the visible body.
+	 *
+	 * Called from the movement tick rather than from input: an animation state
+	 * driven by speed is correct whether the player walked, was pushed, or fell.
+	 * Only switches when the clip changes, because PlayAnimation restarts a clip
+	 * and calling it every frame would freeze the cycle at its first key.
+	 */
+	void UpdateBodyAnimation();
+
+	/** Velocity above which the walk clip plays, in cm/s (0.1 m/s tolerance). */
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Animation")
+	float WalkAnimationThreshold = 10.0f;
+
 	/**
 	 * TEMP QA: scripted walk / reset / pause verification.
 	 *
@@ -109,6 +129,39 @@ protected:
 	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Camera")
 	TObjectPtr<UCameraComponent> FirstPersonCamera;
 
+	/**
+	 * Third-person boom. Collision testing is on, which is what stops the camera
+	 * from ending up inside a wall: the arm shortens until the camera is clear
+	 * instead of clipping through geometry.
+	 */
+	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Camera")
+	TObjectPtr<USpringArmComponent> ThirdPersonArm;
+
+	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Camera")
+	TObjectPtr<UCameraComponent> ThirdPersonCamera;
+
+	/** Boom length in cm: far enough to see the body, close enough to read the street. */
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Camera")
+	float ThirdPersonBoomLength = 340.0f;
+
+	UPROPERTY()
+	TObjectPtr<UAnimSequence> IdleAnimation;
+
+	UPROPERTY()
+	TObjectPtr<UAnimSequence> WalkAnimation;
+
+	/** True while the third-person rig is the active view. */
+	UPROPERTY(BlueprintReadOnly, Category = "Camera")
+	bool bThirdPerson = false;
+
+	/** Clip currently playing on the body, so UpdateBodyAnimation can diff it. */
+	UPROPERTY()
+	TObjectPtr<UAnimSequence> PlayingAnimation;
+
+	/** Toggle-camera action (V). */
+	UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category = "Input")
+	TObjectPtr<UInputAction> ToggleCameraAction;
+
 	/** Degrees per second per unit of mouse input; defaults to Unreal's usual 45. */
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Camera")
 	float LookSensitivity = 45.0f;