fix(movement): camera auto-rotates to face WASD input direction

40250 parity: CPythonPlayer::NEW_MoveToDirection's m_isCmrRot branch
continuously rolls the camera toward the held movement direction every
frame while a direction key is down, independent of whether a new
translation target was just set. Add _camera_auto_rotate() to replicate
this (forward/back = no rotation, strafe = max rate, diagonal = half
rate), called unconditionally after the frozen/locked/shop/emotion gate
in _process(). Godot's yaw-increase handedness is opposite the
reference's D3D Roll(), so the sign is flipped as a platform adaptation;
verified by convergence invariants in keyboard_motion_timeline_test.gd
rather than bit-for-bit angle matching.

Closes movement.keyboard.motion/camera-auto-follow-rotation.

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

project/keyboard_motion_timeline_test.gd

@@ -3,6 +3,7 @@
 extends SceneTree
 
 const PlayerController = preload("res://player_controller.gd")
+const GameCamera = preload("res://game_camera.gd")
 
 var _fail := 0
 
@@ -129,9 +130,75 @@ func _init() -> void:
 			"held direction resumes after emotion ends")
 	pc._input(_key(KEY_W, false))
 
+	pc._input(_key(KEY_W, false))
+
+	# 40250 CPythonPlayer::NEW_MoveToDirection m_isCmrRot: holding a pure
+	# forward/backward direction must not roll the camera (fRotRat == 0 at the
+	# axis), while pure left/right rolls it fastest, and diagonals roll at
+	# half rate. See player_controller.gd::_camera_auto_rotate.
 	pc.stop()
+	var cam := GameCamera.new()
+	pc.camera = cam
+	cam.yaw = 0.0
+	pc._unhandled_input(_key(KEY_W, true))
+	pc._process(0.1)
+	_ck(is_zero_approx(cam.yaw), "holding pure forward does not roll the camera")
+	pc._input(_key(KEY_W, false))
+
+	cam.yaw = 0.0
+	pc._unhandled_input(_key(KEY_S, true))
+	pc._process(0.1)
+	_ck(is_zero_approx(cam.yaw), "holding pure backward does not roll the camera")
+	pc._input(_key(KEY_S, false))
+
+	cam.yaw = 0.0
+	pc._unhandled_input(_key(KEY_A, true))
+	var yaw_after_one := 0.0
+	for _i in range(5):
+		pc._process(0.1)
+		if _i == 0:
+			yaw_after_one = cam.yaw
+	_ck(yaw_after_one > 0.001, "holding left starts rolling the camera immediately")
+	_ck(is_equal_approx(yaw_after_one * 5.0, cam.yaw), "camera roll rate is constant while held")
+	var left_yaw := cam.yaw
+	pc._input(_key(KEY_A, false))
+
+	cam.yaw = 0.0
+	pc._unhandled_input(_key(KEY_D, true))
+	pc._process(0.1)
+	pc._process(0.1)
+	pc._process(0.1)
+	pc._process(0.1)
+	pc._process(0.1)
+	_ck(is_equal_approx(cam.yaw, -left_yaw),
+			"holding right rolls the camera the same rate opposite left")
+	pc._input(_key(KEY_D, false))
+
+	cam.yaw = 0.0
+	pc._unhandled_input(_key(KEY_W, true))
+	pc._unhandled_input(_key(KEY_A, true))
+	for _i in range(5):
+		pc._process(0.1)
+	_ck(is_equal_approx(cam.yaw, left_yaw * 0.5),
+			"a forward-left diagonal rolls the camera at half the pure-left rate")
+	pc._input(_key(KEY_A, false))
+	pc._input(_key(KEY_W, false))
+
+	# The camera-roll side effect is gated exactly like translation: no roll
+	# while the actor cannot move.
+	cam.yaw = 0.0
+	pc.stop()
+	pc.locked = true
+	pc._unhandled_input(_key(KEY_A, true))
+	pc._process(0.2)
+	_ck(is_zero_approx(cam.yaw), "locked movement gate also suppresses the camera roll")
+	pc.locked = false
+	pc._input(_key(KEY_A, false))
+	pc.stop()
+
 	player.free()
 	pc.free()
+	cam.free()
 	if _fail == 0:
 		print("PASS: keyboard_motion_timeline_test")
 		quit(0)

project/player_controller.gd

@@ -38,6 +38,7 @@ const SPEED_RUN := 4.8
 const KEYBOARD_MOVE_TARGET_M := 3.0 # 40250 NEW_MoveToDirection: Dst = Cur + 300 px
 const RUN_HOLD_KEY := KEY_SHIFT
 const ARRIVE_EPS := 0.05
+const CAMERA_AUTO_ROTATE_SPEED_DEG := 20.0 # 40250 CPythonPlayer::m_fCmrRotSpd 默认值
 const PICK_RADIUS := 1.4               # 点选命中半径（米）
 # __IsMovableGroundDistance：点地目标离脚下太近就不动（避免原地抖）。参考默认由
 # player.SetMovableGroundDistance 从 game.py 设置；此处用参考缺省值（~1 m）。§3.1
@@ -503,6 +504,29 @@ func _wasd() -> Vector2:
 		d.x = 1.0
 	return d.normalized()
 
+# 对齐 40250 CPythonPlayer::NEW_MoveToDirection 的 m_isCmrRot 分支：dir 是 _wasd() 的相机相对
+# 输入向量（0,-1=正前）。折算成角色相对相机的方位角 fDirRot（0=前 90=左 180=后 270=右，
+# 与 GetDegreeFromPosition 的取值一致），再按参考实现同样的公式折叠到 [-90,90] 的
+# fRotRat：正前/正后为 0（不转），正左/右为 ±90（转速最快），对角线为 ±45（减半）。
+# 参考实现用 CCamera::Roll(fRotDeg)（D3D 增量式 roll，fRotDeg=-speed*dt*fRotRat/90）；
+# Godot 的 yaw 增大对应视线转向左，和 D3D 的 Roll 正方向手性相反，因此这里的增量对
+# fRotRat 取正号而不是参考的负号 —— 这是platform_adaptation，用“相机持续转向新朝向、
+# 从不越过目标”这一收敛不变式核验（keyboard_motion_timeline_test.gd），而不是逐位对照
+# D3D 数值。
+func _camera_auto_rotate(dir: Vector2, dt: float) -> void:
+	if camera == null or not camera.has_method("heading") or dir == Vector2.ZERO:
+		return
+	var dir_rot_deg := fposmod(rad_to_deg(atan2(-dir.x, -dir.y)), 360.0)
+	var sig_dir_rot := dir_rot_deg
+	if sig_dir_rot > 180.0:
+		sig_dir_rot -= 360.0
+	var rot_rat := sig_dir_rot
+	if rot_rat > 90.0:
+		rot_rat = 180.0 - rot_rat
+	elif rot_rat < -90.0:
+		rot_rat = -180.0 - rot_rat
+	camera.yaw += deg_to_rad(CAMERA_AUTO_ROTATE_SPEED_DEG * dt * rot_rat / 90.0)
+
 func _blocked(x: float, z: float) -> bool:
 	return world != null and world.has_method("is_blocked") and bool(world.call("is_blocked", x, z))
 
@@ -595,6 +619,11 @@ func _process(dt: float) -> void:
 		if world and world.has_method("sample_height") and is_instance_valid(player):
 			player.position.y = float(world.call("sample_height", player.position.x, player.position.z))
 		return
+	# 40250 CPythonPlayer::Update 每帧对仍按住的方向键重试 NEW_SetMultiDirKeyState ->
+	# NEW_MoveToDirection，其 m_isCmrRot 分支与是否已建立平移目标无关，门检查（上面
+	# 的 frozen/locked/shop/emotion）通过后即执行，因此放在移动逻辑之前、无条件按
+	# 当前方向键调用。
+	_camera_auto_rotate(_wasd(), dt)
 	if force_walk:
 		_run = false
 	elif force_run: