fix(rig): curl the fingers, derive the arm angle

Two defects from the 0.2.0 review, both fixed and both measured.

- Fingers splayed because the bind is an A-pose hand. All three joints of all five
  fingers per hand are curled in the standing base (0.28/0.34/0.22 rad), with the
  curl axis probed on the rig first. The front shot now shows relaxed hands.
- The arms-down rotation is derived on every build instead of hard-coded: the
  builder sweeps candidate angles and returns the one whose bone direction points at
  the target (0.60 rad, direction dot 1.000 this build). The old 0.55 was a
  hand-swept constant.
- Base bones are keyed in both clips, so a clip that only animates the limbs cannot
  drop the standing offset.

Regression, recorded rather than hidden: the stride shot shows a standing pose again
after this change. The probe had shown the walk clip playing (speed=28
clip=GigLine_Walk) before it, and pinning the clip to a quarter cycle did not restore
the stride, so the cause needs a fresh look. The shot is retired rather than shipped
broken, and the known-issues table now points at it.

Game/GigLine/Source/GigLine/GigLineShotActor.cpp

@@ -92,6 +92,17 @@ void AGigLineShotActor::UpdateFollowCamera()
 	if (AGigLineCharacter* Character = Cast<AGigLineCharacter>(Pawn))
 	{
 		Character->SetReviewWalk(true);
+		// Park the walk clip at a quarter cycle the first frame of the shot, so the
+		// capture lands mid-stride. Without this the phase is whatever happened to be
+		// playing when the settle timer expired, and a passing pose looks like a still.
+		if (!bFollowPhaseSet)
+		{
+			bFollowPhaseSet = true;
+			if (USkeletalMeshComponent* Body = Character->GetMesh())
+			{
+				Body->SetPosition(0.25f, /*bFireNotifies=*/false);
+			}
+		}
 	}
 	// Offset in the pawn's frame: to its right, slightly above, looking at the
 	// pelvis. Right-of-pawn gives a profile view, which is where a stride reads.
@@ -143,6 +154,7 @@ void AGigLineShotActor::NextShot()
 	// the pawn only holds forward input while a follow shot is being taken, so the
 	// fixed-camera shots later in the list still find it at the spawn point.
 	const bool bFollowThisShot = ShotFollow.IsValidIndex(CurrentShot) && ShotFollow[CurrentShot];
+	bFollowPhaseSet = false;
 	if (AGigLineCharacter* Character = Cast<AGigLineCharacter>(UGameplayStatics::GetPlayerPawn(this, 0)))
 	{
 		Character->SetReviewWalk(bFollowThisShot);