fix(notifications): Advanced Push Rules mode switch keeps highlight/sound tweaks

RuleModeSwitcher rebuilt a rule's actions from scratch, so changing the
mode of e.g. .m.rule.is_user_mention silently dropped its highlight tweak
account-wide. Derive the existing highlight/custom-sound tweaks from the
rule's current actions and pass them through as NotificationModeOptions.
Adds getNotificationModeOptionsFromActions + unit tests.

Fixes #19

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/settings/notifications/PushRuleEditor.tsx

@@ -18,6 +18,7 @@ import { useMatrixClient } from '../../../hooks/useMatrixClient';
 import { AsyncStatus, useAsyncCallback } from '../../../hooks/useAsyncCallback';
 import {
   getNotificationModeActions,
+  getNotificationModeOptionsFromActions,
   NotificationMode,
   useNotificationModeActions,
 } from '../../../hooks/useNotificationMode';
@@ -131,7 +132,13 @@ type RuleModeSwitcherProps = {
 
 function RuleModeSwitcher({ kind, pushRule }: RuleModeSwitcherProps) {
   const mx = useMatrixClient();
-  const getModeActions = useNotificationModeActions();
+  // Preserve any `highlight`/custom sound tweak already on the rule — otherwise
+  // switching mode here rebuilds actions from scratch and silently drops them.
+  const options = useMemo(
+    () => getNotificationModeOptionsFromActions(pushRule.actions),
+    [pushRule.actions],
+  );
+  const getModeActions = useNotificationModeActions(options);
 
   const handleChange = useCallback(
     async (mode: NotificationMode) => {