refactor(ui): migrate 6 meta screens to MetaScreen pattern (Workstream 2)

Relocates main_menu, character_creation, settings_dialog, debug_console,
bug_report_dialog, loading_screen from flat client/ui/ into structured
client/ui/meta/screens/<name>/. All six now extend MetaScreen instead
of Control; the base handles open/close lifecycle, visibility,
captures_input, and — for overlays — the sim-pause contract.

Screen policies set per Tyre's proposal:
- settings_dialog: pauses_sim=false, PUSHES onto MetaStack
- debug_console: pauses_sim=true, PUSHES (D-088 routing via base)
- bug_report_dialog: pauses_sim=true, PUSHES
- loading_screen: closable_by_escape=false, PUSHES
- main_menu, character_creation: scene-roots, extend MetaScreen for
  the lifecycle contract only, do NOT push onto the stack

character_creation stays at its current surface (tabs, descriptor,
creation_confirmed signal unchanged). Tab consolidation and
CharacterProfile migration happen in Workstreams 5 and 6.

Knock-on changes:
- main.tscn ModalLayer CanvasLayer renamed to MetaLayer; main.gd
  @onready refs updated; constants.gd comment updated; test_client_p3
  and test_ui_framework_sprint15 assertions updated; test_monologue_display
  and .tscn header comments updated.
- OPEN_MENU handler now pushes settings_dialog onto MetaStack before
  calling open(). Full ESC priority chain lands in Workstream 4.
- atlas_app.gd: _unhandled_key_input signature widened from
  InputEventKey to InputEvent with an is-check, per Godot 4 API. Pre-
  existing narrowing was silently tolerated until main.tscn started
  fully instantiating under the new pattern.
- test_client_p3: entity_renderer type annotations corrected from
  ColorRect to Sprite2D (stale since a prior refactor); facing
  indicator rotation assertion switched to angle_difference() for
  modular-safe comparison.

Verification:
- gdlint client/scripts/ client/ui/ — zero problems
- godot --headless --path client --quit — no SCRIPT ERROR
- test_client_p3: 24/24 pass
- test_ui_framework_sprint15: 54/54 pass
- test_implant_nav_stack: 52/52 pass
- test_implant_registry: 42/42 pass
- test_implant_app_lifecycle: 36/36 pass

Workstream 1 foundation (84105916) remains unchanged. Workstreams 3-8
follow: protocol layer, Option A sequencing, 3-tab restructure,
Bookmark tab, location picker, Skills stub.

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

client/tests/test_client_p3.gd

@@ -124,7 +124,7 @@ func test_z_ui_layer_above_world() -> void:
 	var inst := _make_scene()
 	var ui_layer = inst.get_node("UILayer") as CanvasLayer
 	var insert_layer = inst.get_node("InsertOverlay") as CanvasLayer
-	var modal_layer = inst.get_node("ModalLayer") as CanvasLayer
+	var modal_layer = inst.get_node("MetaLayer") as CanvasLayer
 	assert_that(insert_layer.layer).override_failure_message(
 		"InsertOverlay must be CanvasLayer %d" % Constants.CANVAS_INSERT
 	).is_equal(Constants.CANVAS_INSERT)
@@ -132,13 +132,13 @@ func test_z_ui_layer_above_world() -> void:
 		"UILayer must be CanvasLayer %d" % Constants.CANVAS_UI
 	).is_equal(Constants.CANVAS_UI)
 	assert_that(modal_layer.layer).override_failure_message(
-		"ModalLayer must be CanvasLayer %d" % Constants.CANVAS_MODAL
+		"MetaLayer must be CanvasLayer %d" % Constants.CANVAS_MODAL
 	).is_equal(Constants.CANVAS_MODAL)
 	assert_that(ui_layer.layer > insert_layer.layer).override_failure_message(
 		"UILayer must render above InsertOverlay"
 	).is_true()
 	assert_that(modal_layer.layer > ui_layer.layer).override_failure_message(
-		"ModalLayer must render above UILayer"
+		"MetaLayer must render above UILayer"
 	).is_true()
 
 
@@ -168,7 +168,7 @@ func test_entity_lerp_moves_toward_target() -> void:
 	var entity := [{"entity_id": 11, "x": 5.0, "y": 5.0, "z": 0,
 		"kind": {"variant": "Npc", "data": null}}]
 	renderer.update_entities(entity)
-	var node: ColorRect = renderer.entity_nodes[11]
+	var node: Sprite2D = renderer.entity_nodes[11]
 	var start_pos: Vector2 = node.position
 	# Move target to (6, 5)
 	var entity_moved := [{"entity_id": 11, "x": 6.0, "y": 5.0, "z": 0,
@@ -212,7 +212,7 @@ func test_entity_lerp_converges_within_300ms() -> void:
 	# Simulate 0.3s at 60fps (18 frames × 0.016s ≈ 0.288s)
 	for i in 20:
 		renderer._process(0.016)
-	var final_node: ColorRect = renderer.entity_nodes[12]
+	var final_node: Sprite2D = renderer.entity_nodes[12]
 	var final_pos: Vector2 = final_node.position
 	# Should be within 5% of target (97% convergence at 0.3s)
 	var dist: float = final_pos.distance_to(target)
@@ -272,9 +272,10 @@ func test_facing_indicator_rotation_matches_input_mapper_angle() -> void:
 	for angle in angles:
 		InputMapper.facing_angle = angle
 		renderer.update_entities(entity)
-		assert_that(indicator.rotation).override_failure_message(
-			"angle %.3f: expected rotation %.3f, got %.3f" % [angle, angles[angle], indicator.rotation]
-		).is_equal_approx(angles[angle], 0.001)
+		var diff := absf(angle_difference(indicator.rotation, angles[angle]))
+		assert_that(diff).override_failure_message(
+			"angle %.3f: expected rotation %.3f, got %.3f (diff %.4f)" % [angle, angles[angle], indicator.rotation, diff]
+		).is_less_equal(0.001)
 	InputMapper.facing_angle = -PI / 2.0  # Reset to default
 	renderer.queue_free()
 
@@ -292,7 +293,7 @@ func test_lerp_weight_increases_with_delta() -> void:
 		"kind": {"variant": "Npc", "data": null}}]
 	renderer.update_entities(entity_moved)
 	# Small delta step
-	var small_node: ColorRect = renderer.entity_nodes[20]
+	var small_node: Sprite2D = renderer.entity_nodes[20]
 	var small_start: float = small_node.position.x
 	renderer._process(0.008)
 	var small_progress: float = small_node.position.x - small_start

client/tests/test_monologue_display.gd

@@ -472,7 +472,7 @@ func test_monologue_display_parented_to_canvas_layer_20_in_main_scene() -> void:
 	## D-049: Structural verification — MonologueDisplay must be a direct child of
 	## UILayer (CanvasLayer, layer=20) in the live scene tree, not the world layer.
 	## Catches regressions where the node gets accidentally moved to InsertOverlay
-	## (layer=10) or ModalLayer (layer=30), or dropped into the world z-stack.
+	## (layer=10) or MetaLayer (layer=30), or dropped into the world z-stack.
 	##
 	## Scene path verified: Game/UILayer/MonologueDisplay (main.tscn line 141).
 	if not ResourceLoader.exists("res://scenes/main.tscn"):

client/tests/test_ui_framework_sprint15.gd

@@ -66,13 +66,13 @@ func test_ui_layer_is_canvas_layer_20() -> void:
 
 
 func test_modal_layer_is_canvas_layer_30() -> void:
-	# D-049: ModalLayer = pause/inventory modal scope = CanvasLayer 30.
+	# D-049: MetaLayer = pause/inventory modal scope = CanvasLayer 30.
 	var scene := MAIN_SCENE
 	_instance = scene.instantiate()
 	auto_free(_instance)
 	add_child(_instance)
 
-	var modal_layer: CanvasLayer = _instance.get_node("ModalLayer")
+	var modal_layer: CanvasLayer = _instance.get_node("MetaLayer")
 	assert_that(modal_layer).is_not_null()
 	assert_that(modal_layer.layer).is_equal(Constants.CANVAS_MODAL)
 
@@ -83,7 +83,7 @@ func test_ui_layer_above_insert_overlay() -> void:
 
 
 func test_modal_layer_above_ui_layer() -> void:
-	# D-049: ModalLayer (30) must render above UILayer (20).
+	# D-049: MetaLayer (30) must render above UILayer (20).
 	assert_that(Constants.CANVAS_MODAL).is_greater(Constants.CANVAS_UI)