Make Main, Settings, ChooseScene, and gameplay run in Godot 4.6

Catch-all commit for everything the --convert-3to4 tool missed during a
manual playtest of the game. All errors raised by clicking through Main
-> Puzzles -> level were fixed.

GDScript:
- PackedScene.instance() -> instantiate() (ChooseScene.gd)
- String(x) constructor doesn't exist -> str(x) (MBase, MScene,
  MLevel, Animation, Levels)
- 'x as int/String/bool' doesn't parse strings -> explicit
  int()/str()/bool(int()) (MScene, MLevel, MSetting)
- BaseButton.pressed (property) -> button_pressed; set_pressed() ->
  direct assignment (Settings.gd)
- AnimationPlayer.add_animation() removed -> go through
  AnimationLibrary (Levels.gd)
- PhysicsDirectSpaceState3D.intersect_ray(from, to, ...) ->
  PhysicsRayQueryParameters3D.create() (Levels.gd)
- @export with type-hint-in-comment ('# (String, ...)') -> explicit
  @export_enum (candle.gd)
- Get effective material with get_active_material() instead of
  get_surface_override_material(), with null guard (Levels.gd)
- get_node() -> get_node_or_null() so missing items from ahog.json
  (e.g. sm_super_dager in Home) don't crash (Levels.gd)

Scenes/resources:
- Remove 14 Tween nodes from WarCraft.tscn — Tween is no longer a
  Node in Godot 4. Rewrite Animation.start_dissolve to use
  create_tween().tween_method().
- Rename property material/N -> surface_material_override/N in every
  .tscn (10 files) — Godot 3 -> 4 rename that --convert-3to4 missed.
  Without this, MeshInstance3D.get_active_material(0) returned the
  glTF-imported StandardMaterial3D instead of the project's custom
  dissolve ShaderMaterial.

Shaders:
- One-shot scripts/migrate_shaders.gd walks every .material under
  assets/ and fixes Godot 3 -> 4 shader code in-place. Fixed 17
  materials: depth_draw_alpha_prepass -> depth_prepass_alpha,
  hint_color -> source_color, NORMALMAP -> NORMAL_MAP.

Result: Main, Settings, ChooseScene, and the WarCraft level all run
without script or shader errors. Remaining noise is non-blocking
(visual_shader graph in text_outline.material, baked lightmap binary
format from Godot 3, and empty animation tracks).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/migrate_shaders.gd

@@ -0,0 +1,61 @@
+@tool
+extends SceneTree
+
+# One-shot migration tool: walk every .material file, fix Godot 3 shader code
+# to Godot 4 syntax, save back.
+#
+# Run with: godot --headless --script scripts/migrate_shaders.gd
+
+const REPLACEMENTS := [
+	["depth_draw_alpha_prepass", "depth_prepass_alpha"],
+	["hint_color", "source_color"],
+	["hint_albedo", "source_color"],
+	["hint_black_albedo", "source_color"],
+	["hint_white", ""],
+	["hint_black", ""],
+	["hint_aniso", "hint_anisotropy"],
+	["NORMALMAP", "NORMAL_MAP"],
+]
+
+func _init() -> void:
+	var fixed := 0
+	var checked := 0
+	for path in _find_materials("res://assets"):
+		checked += 1
+		var mat = ResourceLoader.load(path, "", ResourceLoader.CACHE_MODE_IGNORE)
+		if mat == null:
+			continue
+		if mat is ShaderMaterial and mat.shader != null:
+			var old_code: String = mat.shader.code
+			var new_code := old_code
+			for pair in REPLACEMENTS:
+				new_code = new_code.replace(pair[0], pair[1])
+			if new_code != old_code:
+				mat.shader.code = new_code
+				var err = ResourceSaver.save(mat, path)
+				if err == OK:
+					fixed += 1
+					print("FIXED ", path)
+				else:
+					push_error("Failed to save " + path + " (err=" + str(err) + ")")
+	print("Done. checked=", checked, " fixed=", fixed)
+	quit()
+
+func _find_materials(dir_path: String) -> Array:
+	var result := []
+	var dir = DirAccess.open(dir_path)
+	if dir == null:
+		return result
+	dir.list_dir_begin()
+	var name = dir.get_next()
+	while name != "":
+		if name == "." or name == "..":
+			name = dir.get_next()
+			continue
+		var sub = dir_path + "/" + name
+		if dir.current_is_dir():
+			result.append_array(_find_materials(sub))
+		elif name.ends_with(".material") or name.ends_with(".tres"):
+			result.append(sub)
+		name = dir.get_next()
+	return result