gmp(M02): add player input intent seam

Work-Package: M02-GMP-INPUT-001
Agent: sindo-main-codex
Tests: verify_player_input; renderer baseline dry-run; coordinate, streaming, documentation and coordination gates
Fidelity: preserves current sandbox bindings and movement/camera behavior; exact build-12340 semantics remain unverified

src/tests/scenes/player_input_regression.tscn

@@ -0,0 +1,14 @@
+[gd_scene load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://src/scenes/player/third_person_wow_controller.gd" id="1_player"]
+
+[node name="PlayerInputRegression" type="CharacterBody3D"]
+script = ExtResource("1_player")
+spawn_at_tile_center = false
+character_model_path = ""
+
+[node name="Visual" type="Node3D" parent="."]
+
+[node name="CameraPivot" type="Node3D" parent="."]
+
+[node name="Camera3D" type="Camera3D" parent="CameraPivot"]