#84: move 215 root files into a folder hierarchy

Everything lived in one flat directory, so a diff gave no clue what area it
touched and finding the file you wanted meant knowing its exact name. Twelve
folders now, grouped by what a thing IS rather than what type it is - a
vessel's definition, its component scenes and its upgrade resources sit
together, because that is the set you read when you change one of them.

  buildings  core  controllers  enemies  logistics  planets
  resources  shaders  surface  ui  vessels  vfx  world

332 files moved and every res:// reference rewritten - 306 files touched,
including the autoload and main-scene paths in project.godot. Nothing renamed:
this is purely where files sit, so the diff is a pile of pure moves and no
behaviour is buried in it. ui_theme.tres, icon.svg and web_shell.html stay at
the root, where Godot and the export preset expect them.

Verified three ways, because a suite alone would not have caught all of it:
the full 117 pass, the web export builds clean, and the game renders.

The export is why that matters. The FIRST export after the move failed with
"Attempt to open script 'res://GameState.gd'" - the old path - while
project.godot on disk plainly said res://core/GameState.gd. That is this
project's documented Android FUSE mtime trap: Godot served a cached copy of a
file whose content had changed. A `touch` fixed it. Nothing in the test suite
would have found that, because the suite runs from a copy on a native
filesystem - the one place the bug cannot happen.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

surface/PlanetSurfaceController.gd

@@ -0,0 +1,93 @@
+extends Node2D
+
+const SURFACE_PROFILES = preload("res://surface/PlanetSurfaceProfiles.gd")
+const PLANET_DEFINITIONS = preload("res://planets/PlanetDefinitions.gd")
+const PLANET_SETUPS = preload("res://surface/PlanetSetups.gd")
+const SETUP_HOST_SCENE: PackedScene = preload("res://surface/PlanetSetupHost.tscn")
+
+# Bootstraps the surviving fleet, including each vessel type, on this scene's
+# own startup (from GameState, since this is a fresh scene tree - nothing here
+# carries over automatically) and handles the always-available exit prompt that
+# fades back out to Main.tscn, restoring the fleet at wherever it left
+# space from.
+
+@export var fade_duration: float = 0.4
+
+@onready var fleet: Node2D = get_node("../Fleet")
+@onready var camera: Camera2D = get_node("../Camera2D")
+@onready var planet_name_label: Label = get_node("../UI/PlanetNameLabel")
+@onready var exit_button: IconButton = get_node("../UI/ExitButton")
+@onready var fade_rect: ColorRect = get_node("../FadeOverlay/FadeRect")
+@onready var background: ColorRect = get_node("../BackgroundLayer/Background")
+@onready var feature_host: Node2D = get_node("../SurfaceFeatures")
+
+var transitioning: bool = false
+
+
+func _ready() -> void:
+	var planet_definition: Resource = PLANET_DEFINITIONS.get_definition(GameState.planet_definition_id)
+	_compose_surface(SURFACE_PROFILES.get_profile(planet_definition.surface_profile_id))
+	fleet.spawn_ships(GameState.surviving_ship_count, Vector2.ZERO,
+		GameState.surviving_vessel_types)
+	camera.position = Vector2.ZERO
+	camera.zoom = Vector2(GameState.return_camera_zoom, GameState.return_camera_zoom)
+	planet_name_label.text = GameState.planet_name
+	exit_button.pressed.connect(_on_exit_pressed)
+
+	fade_rect.color.a = 1.0
+	var tween: Tween = create_tween()
+	tween.tween_property(fade_rect, "color:a", 0.0, fade_duration)
+
+
+func _compose_surface(profile: Resource) -> void:
+	# Shared with PlanetSetupEditor, deliberately: the backdrop is one
+	# instanced scene configured through one method, so what an author sees
+	# while placing markers is what a player sees after landing. See the
+	# header of SurfaceBackground.gd.
+	background.apply_profile(profile)
+	for caption_path in ["../UI/BankCaption", "../UI/FleetCaption", "../UI/CaptureLabel"]:
+		var caption: Label = get_node(caption_path)
+		caption.add_theme_color_override("font_color", profile.caption_color)
+		caption.add_theme_color_override("font_outline_color", profile.caption_outline_color)
+	if profile.features_scene != null:
+		var features: Node = profile.features_scene.instantiate()
+		feature_host.add_child(features)
+
+	var setup: Resource = PLANET_SETUPS.setup_for_planet(GameState.planet_id, profile.profile_id)
+	if setup != null:
+		# Untyped on purpose: a static PlanetSetupHost annotation here would
+		# need the global class_name cache to already know about it, which
+		# is only true after an editor/import pass has run (see #31/#35's
+		# load-order notes) - a plain Node reference plus duck-typed
+		# apply_setup() sidesteps that entirely, same as BuildingDefinitions
+		# and VesselDefinitions already do for their own resource types.
+		var setup_host: Node = SETUP_HOST_SCENE.instantiate()
+		feature_host.add_child(setup_host)
+		setup_host.apply_setup(setup)
+	else:
+		# No PlanetSetup exists for this profile at all (#55: "void" has
+		# none authored) - register zero required points directly, rather
+		# than leaving this planet's conquest state unregistered forever.
+		# capture_state()'s fallback for an unregistered planet_id defaults
+		# to conquered=false (see test_planet_conquest_gate.gd's own "a
+		# fresh planet reported conquered" check), which would otherwise
+		# permanently block extractor placement here - register_capture_
+		# points() treats a total of 0 as vacuously already conquered.
+		GameState.register_capture_points(GameState.planet_id, 0)
+
+
+func _on_exit_pressed() -> void:
+	if transitioning:
+		return
+	transitioning = true
+
+	GameState.surviving_ship_count = fleet.ships.size()
+	GameState.surviving_vessel_types = fleet.vessel_types()
+
+	var tween: Tween = create_tween()
+	tween.tween_property(fade_rect, "color:a", 1.0, fade_duration)
+	tween.tween_callback(_return_to_space)
+
+
+func _return_to_space() -> void:
+	get_tree().change_scene_to_file("res://world/Main.tscn")