Complete M11 Creator Studio and M12 Trust & Safety for PC5

- Creator Studio: Visual behavior & property inspector, GLB model importer, binary persistence
- Trust & Safety: 18+ TOS confirmation (DOB removed), creator guidelines & briefing card on join, in-game reporting HUD
- Test Harness: Add --filter, --skip-backend, --skip-godot to run_checkpoint_tests.py

scripts/discovery_ui.gd

@@ -1,5 +1,8 @@
 extends Control
 class_name DiscoveryUI
+
+const WorldBriefingModal = preload("res://scripts/world_briefing_modal.gd")
+
 ## Discovery & Home Screen for browsing, searching, and entering experiences.
 ##
 ## docs/planning/discovery.md (task b77bddf31ba5).
@@ -244,7 +247,7 @@ func _create_world_card(world: DiscoveryApiClient.WorldSummary) -> Control:
 	var enter_button := Button.new()
 	enter_button.text = "Enter World"
 	enter_button.custom_minimum_size = Vector2(110, 30)
-	enter_button.pressed.connect(_on_enter_world_pressed.bind(world.id, enter_button))
+	enter_button.pressed.connect(_show_world_briefing.bind(world, enter_button))
 	title_row.add_child(enter_button)
 	vbox.add_child(title_row)
 
@@ -302,6 +305,20 @@ func _update_pagination() -> void:
 		next_button.disabled = ((_current_page + 1) >= total_pages)
 
 
+func _show_world_briefing(world: DiscoveryApiClient.WorldSummary, button: Button) -> void:
+	var modal := WorldBriefingModal.new()
+	modal.setup_world_data(
+		world.id,
+		world.name,
+		world.owner_username,
+		world.content_guidelines,
+		world.tags,
+		world.play_count
+	)
+	modal.entered_confirmed.connect(func(target_wid: int): _on_enter_world_pressed(target_wid, button))
+	add_child(modal)
+
+
 func _on_enter_world_pressed(world_id: int, button: Button) -> void:
 	button.disabled = true
 	button.text = "Joining…"