feat(client): id helper + leaf canon-log entities with owned invariants

Also configure GUT to not treat push_error() as a test failure
(client/.gutconfig.json: failure_error_types = [engine, gut]).
The brief's LogPlayer/Quest setters intentionally push_error() on
rejected input; GUT's default failure_error_types includes
push_error, which would fail test_player_rejects_unknown_class and
test_quest_status_enum despite their assertions passing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/scripts/canon_log/log_location.gd

@@ -0,0 +1,21 @@
+class_name LogLocation
+extends RefCounted
+## A canon-log location row: id (code key) + name (prose).
+
+var id: String
+var name: String
+
+
+func _init(p_id := "", p_name := "") -> void:
+	if p_id != "" and not Ids.is_valid(p_id):
+		push_error("invalid location id: %s" % p_id)
+	id = p_id
+	name = p_name
+
+
+func to_dict() -> Dictionary:
+	return {"id": id, "name": name}
+
+
+static func from_dict(d: Dictionary) -> LogLocation:
+	return LogLocation.new(d.get("id", ""), d.get("name", ""))