feat: config object migration path and add new options to settings

Plugins/ZShell/Config/migration.hpp

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <QJsonObject>
+#include <QStringList>
+
+namespace ZShell::config {
+
+// A single migration rule: move the value stored at the dotted `from` path
+// to the dotted `to` path, then delete the old key (and any parent objects
+// left empty).
+//
+// Rules are applied to the raw JSON file on every load, before the schema
+// loads it. They are idempotent: once the old key is gone the rule never
+// fires again, so no version stamping is needed. Old rules can stay in the
+// table forever.
+//
+// WARNING: the target path must exist in the schema (i.e. a ConfigObject
+// property somewhere in the tree). If it does not, the migrated value is
+// loaded as an unknown key and silently dropped on the next save.
+struct ConfigMigrationRule {
+	QString from;
+	QString to;
+};
+
+// Helper for writing rules: migrate("general.color.foo", "display.bar.foo")
+inline ConfigMigrationRule migrate(const QString& from, const QString& to) {
+	return {from, to};
+}
+
+class ConfigMigrations {
+	public:
+	[[nodiscard]] static const QList<ConfigMigrationRule>& rules();
+
+	// Applies all rules to `json`, returning the migrated object.
+	[[nodiscard]] static QJsonObject apply(const QJsonObject& json);
+};
+
+} // namespace ZShell::config