fix(ui): correct Sprite2D/self_modulate assertions in P2 client tests (#574)

Same Sprite2D correction applied to test_client_p2.gd entity color tests
(Terrain, Player) — ColorRect was replaced with Sprite2D in entity_renderer.gd.
Minor comment clarification in test_rendering.gd rotation test.

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

client/tests/test_rendering.gd

@@ -326,7 +326,7 @@ func test_entity_renderer_facing_indicator_rotation_accuracy() -> void:
 		PI / 2.0: PI,                       # South
 		3.0 * PI / 4.0: 5.0 * PI / 4.0,    # Southwest (raw: 3PI/4 + PI/2 = 5PI/4)
 		PI: 3.0 * PI / 2.0,                 # West (raw: PI + PI/2 = 3PI/2)
-		-3.0 * PI / 4.0: -PI / 4.0,        # Northwest (-3PI/4 + PI/2 = -PI/4)
+		-3.0 * PI / 4.0: -PI / 4.0,        # Northwest: wraps negative — Godot returns raw un-normalised rotation
 	}
 	renderer.update_entities(_test_entities_v2)
 	var player_node = renderer.entity_nodes[1]