Remove CCS viewport letterboxing

tests/ccs_cases_2_ui_test.gd

@@ -91,12 +91,13 @@ func _run() -> void:
 	_assert(screen.active_scene.is_computer_open(), "the computer launcher should open the simulated desktop")
 	_assert(not screen.active_scene.computer_launcher.visible, "the launcher should hide while the computer is open")
 	_assert(screen.active_scene.computer_overlay.get_node("Screen").texture.resource_path.ends_with("computer-base.png"), "the overlay should render the supplied computer base")
-	_assert(screen.active_scene.computer_overlay.get_node("Screen").stretch_mode == TextureRect.STRETCH_KEEP_ASPECT_CENTERED, "the computer should be fully contained without cropping")
+	_assert(screen.active_scene.computer_overlay.get_node("Screen").stretch_mode == TextureRect.STRETCH_SCALE, "the computer should fill the viewport without side bars")
 	_assert(screen.close_transient_overlay(), "Escape routing should close the computer before the pause menu")
 	_assert(not screen.active_scene.is_computer_open(), "closing the transient overlay should restore the doctor office")
 	_assert(not screen.close_transient_overlay(), "a second Escape should be available to open the pause menu")
 	_assert(is_equal_approx(screen.DESIGN_SIZE.x / screen.DESIGN_SIZE.y, 16.0 / 9.0), "the graphical CCS stage should use a true 16:9 design canvas")
-	_assert(is_equal_approx(screen.stage_root.scale.x, screen.stage_root.scale.y), "the graphical stage should preserve its aspect ratio")
+	_assert(screen.stage_root.size.is_equal_approx(screen.size), "the graphical stage should fill the available viewport")
+	_assert(screen.stage_root.position.is_equal_approx(Vector2.ZERO), "the graphical stage should not introduce letterbox margins")
 	var stale_graphical_attempt := _sample_attempt(false)
 	stale_graphical_attempt.experienceMode = "graphical_interview"
 	stale_graphical_attempt.openingCompleted = true