Rebrand remaining user-visible Grok strings to Kigi/Kimi

The welcome hero subtitle still read "Thanks for trying Grok Build";
theme display names, the NO_COLOR/COLORTERM diagnostics notes, the
permission notification title, the self-update restart hints, and the
clipboard-wrap protocol marker all still said Grok. Canonical theme keys
(groknight/grokday) are unchanged — only display strings move.

crates/codegen/kigi-tui/src/app/acp_handler/permissions.rs

@@ -74,7 +74,7 @@ pub(super) fn handle_permission_request(
     {
         app.notification_service.notify(NotificationEvent {
             kind: NotificationEventKind::ApprovalRequired,
-            title: "Grok".into(),
+            title: "Kigi".into(),
             body: NotificationEventKind::ApprovalRequired.as_str().into(),
             session_id: Some(perm.request.session_id.0.to_string()),
         });