feat(client): mouse-relative facing and movement (#526, D-054)

Mouse position now determines facing direction as a client-side float.
WASD remapped: W=toward cursor, S=away, A/D=strafe. Facing octant
derived from mouse angle and sent to server via SET_FACING action only
when it changes. EntityRenderer facing indicator uses continuous angle
for smooth rotation. SimBridge test mode updated to handle SetFacing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/scripts/autoloads/input_mapper.gd

@@ -3,7 +3,11 @@ extends Node
 # Semantic actions — NO raw key codes cross the bridge
 # Movement uses hold-to-move (polled each frame in _process).
 # Discrete actions (interact, stance, etc.) use press events (_unhandled_input).
-# Composite diagonals: holding W+D simultaneously → northeast.
+#
+# D-054: Mouse-relative facing and movement.
+# Mouse position determines facing direction (client-side float).
+# WASD is relative to facing: W = toward cursor, S = away, A/D = strafe.
+# Server receives facing octant only — the full float stays client-side.
 #
 # Movement throttle: client-side rate limit per stance (D-053).
 # Sprint=5/s, Walk=2.5/s, Careful=1.7/s, Crouch=1.25/s.
@@ -15,10 +19,17 @@ enum Action {
 	INTERACT, USE_PERCEPTION_MODE, OPEN_MENU, PAUSE, UNPAUSE,
 	TOGGLE_STANCE_UP, TOGGLE_STANCE_DOWN,
 	BUG_REPORT,  # #495: F12 WRONG button — client-only, not sent to server
+	SET_FACING,  # D-054: facing octant update (no movement)
 }
 
 var input_queue: Array[Dictionary] = []
 
+# D-054: Client-side facing angle (radians). 0=East, -PI/2=North, PI/2=South.
+# Updated every frame from mouse position. EntityRenderer reads this for indicator.
+var facing_angle: float = -PI / 2.0  # Default: North
+var facing_octant: String = "North"   # Derived from facing_angle
+var _last_sent_octant: String = "North"  # Track to avoid redundant sends
+
 # Minimum milliseconds between movement commands, per stance.
 # Tuned so Walk feels like walking, Sprint feels fast but readable.
 const MOVE_INTERVAL_MS := {
@@ -31,27 +42,44 @@ var _last_move_msec: int = 0
 
 
 # Hold-to-move: poll held direction keys each frame, throttled by stance.
+# D-054: WASD is now mouse-relative. W = toward cursor, A/D = strafe.
 # Server-side cooldown (D-053) is authoritative; this prevents client flooding.
 # D-064: movement suppressed during dialogue (walk-away handled by dialogue_box).
 func _process(_delta: float) -> void:
+	# D-054: Update facing angle from mouse position every frame
+	_update_facing_from_mouse()
+
 	if GameState.dialogue_active:
 		return
-	var dir := Vector2i.ZERO
-	if Input.is_action_pressed("move_north"):
-		dir.y -= 1
-	if Input.is_action_pressed("move_south"):
-		dir.y += 1
-	if Input.is_action_pressed("move_east"):
-		dir.x += 1
-	if Input.is_action_pressed("move_west"):
-		dir.x -= 1
 
-	if dir != Vector2i.ZERO:
+	# D-054: Send facing octant to server when it changes (even without movement)
+	if facing_octant != _last_sent_octant:
+		_last_sent_octant = facing_octant
+		input_queue.append({
+			"action": Action.SET_FACING,
+			"timestamp_msec": Time.get_ticks_msec(),
+			"action_data": {"facing": facing_octant},
+		})
+
+	# Poll held WASD keys
+	var raw_dir := Vector2i.ZERO
+	if Input.is_action_pressed("move_north"):
+		raw_dir.y -= 1
+	if Input.is_action_pressed("move_south"):
+		raw_dir.y += 1
+	if Input.is_action_pressed("move_east"):
+		raw_dir.x += 1
+	if Input.is_action_pressed("move_west"):
+		raw_dir.x -= 1
+
+	if raw_dir != Vector2i.ZERO:
 		var now := Time.get_ticks_msec()
 		var interval: int = MOVE_INTERVAL_MS.get(GameState.player_stance, 200)
 		if now - _last_move_msec >= interval:
 			_last_move_msec = now
-			var action: Action = _dir_to_action(dir)
+			# D-054: Transform WASD input relative to mouse facing
+			var world_dir := _wasd_to_world_dir(raw_dir)
+			var action: Action = _dir_to_action(world_dir)
 			input_queue.append({
 				"action": action,
 				"timestamp_msec": now,
@@ -92,6 +120,76 @@ func flush_queue() -> Array[Dictionary]:
 	return queue
 
 
+# D-054: Compute facing angle from mouse position relative to player screen position.
+# Uses viewport canvas transform to convert world coords to screen coords.
+func _update_facing_from_mouse() -> void:
+	var vp := get_viewport()
+	if vp == null:
+		return
+	var canvas_xf := vp.get_canvas_transform()
+	var player_world_px := GameState.player_position * Constants.TILE_SIZE
+	var player_screen := canvas_xf * player_world_px
+	var mouse_screen := vp.get_mouse_position()
+	var delta := mouse_screen - player_screen
+	# Only update if mouse is meaningfully distant from player (avoid jitter at center)
+	if delta.length_squared() > 4.0:
+		facing_angle = delta.angle()
+		facing_octant = _angle_to_octant(facing_angle)
+
+
+# D-054: Transform raw WASD input (screen-space) to world direction relative to mouse facing.
+# W (+Y up in input, mapped to forward), S (backward), A (strafe left), D (strafe right).
+# Raw input: W=(-Y), S=(+Y), A=(-X), D=(+X) in screen coords.
+# Forward = facing_angle direction. Output: nearest octant direction vector.
+func _wasd_to_world_dir(raw_dir: Vector2i) -> Vector2i:
+	# Build a continuous direction vector relative to facing.
+	# raw_dir.y: -1 = W (forward), +1 = S (backward)
+	# raw_dir.x: -1 = A (strafe left), +1 = D (strafe right)
+	var forward := Vector2(cos(facing_angle), sin(facing_angle))
+	var right := Vector2(-forward.y, forward.x)  # 90° clockwise
+
+	# Combine: forward/back from W/S, strafe from A/D
+	var world_float := forward * float(-raw_dir.y) + right * float(raw_dir.x)
+
+	# Snap to nearest octant direction
+	return _snap_to_octant_dir(world_float)
+
+
+# Snap a floating-point direction vector to the nearest of 8 cardinal/diagonal directions.
+static func _snap_to_octant_dir(dir: Vector2) -> Vector2i:
+	if dir.length_squared() < 0.001:
+		return Vector2i.ZERO
+	var angle := dir.angle()
+	# Quantize to nearest 45° (PI/4)
+	var octant := roundi(angle / (PI / 4.0))
+	match octant:
+		0: return Vector2i(1, 0)        # East
+		1: return Vector2i(1, 1)        # Southeast
+		2, -6: return Vector2i(0, 1)    # South
+		3, -5: return Vector2i(-1, 1)   # Southwest
+		4, -4: return Vector2i(-1, 0)   # West
+		-3, 5: return Vector2i(-1, -1)  # Northwest
+		-2: return Vector2i(0, -1)      # North
+		-1: return Vector2i(1, -1)      # Northeast
+		_: return Vector2i.ZERO
+
+
+# D-054: Convert a facing angle (radians) to the nearest octant name.
+# Godot 2D: 0=East, PI/2=South, -PI/2=North.
+static func _angle_to_octant(angle: float) -> String:
+	var octant := roundi(angle / (PI / 4.0))
+	match octant:
+		0: return "East"
+		1: return "Southeast"
+		2, -6: return "South"
+		3, -5: return "Southwest"
+		4, -4: return "West"
+		-3, 5: return "Northwest"
+		-2: return "North"
+		-1: return "Northeast"
+		_: return "East"
+
+
 # Map a direction vector to the corresponding movement Action.
 # Handles all 8 directions via composite W+D, W+A, etc.
 static func _dir_to_action(dir: Vector2i) -> Action: