fix: make session ordering follow activity lifecycle

Session lists now promote a conversation when it starts working and again when it settles, instead of reacting to every streaming timestamp update. This keeps ordering responsive without bringing back the sidebar churn removed by the recent performance work.

Apply the same user-visible order across Recent, project and worktree groups, session switchers, mobile navigation, widgets, the command palette, and the desktop tray. Preserve pinned priority, freeze timestamp fallback ordering, and keep child-session activity scoped to siblings under the same parent so it never moves the root conversation.

Seed reconnect snapshots without synthetic jumps, clear ephemeral ranks on deletion and runtime changes, and cover lifecycle transitions, mixed root/child trees, metadata-only updates, and project-group ordering with regression tests.

packages/ui/src/apps/MobileSessionsSheet.tsx

@@ -49,7 +49,13 @@ import { mergeLiveSessionWithGlobalSession, refreshGlobalSessions, useGlobalSess
 import { useMobileSessionExpansionStore } from '@/stores/useMobileSessionExpansionStore';
 import { useMobileSessionTreeStore } from '@/stores/useMobileSessionTreeStore';
 import { useProjectsStore } from '@/stores/useProjectsStore';
+import { useSessionPinnedStore } from '@/stores/useSessionPinnedStore';
 import { orderWorktrees, useWorktreeOrderStore } from '@/stores/useWorktreeOrderStore';
+import {
+  EMPTY_SESSION_ORDER_RANKS,
+  orderSessionsByLifecycleScopes,
+  useSessionOrderingStore,
+} from '@/sync/session-ordering';
 import { useSessionUIStore } from '@/sync/session-ui-store';
 import { useAllLiveSessions } from '@/sync/sync-context';
 import type { WorktreeMetadata } from '@/types/worktree';
@@ -65,6 +71,8 @@ type MobileSessionsSheetProps = {
   variant?: 'sheet' | 'sidebar';
 };
 
+const EMPTY_PINNED_SESSION_IDS = new Set<string>();
+
 type ProjectMeta = {
   id: string;
   label: string;
@@ -519,6 +527,14 @@ export const MobileSessionsSheet: React.FC<MobileSessionsSheetProps> = ({ open,
   const { git } = useRuntimeAPIs();
   const liveSessions = useAllLiveSessions();
   const globalActiveSessions = useGlobalSessionsStore((state) => state.activeSessions);
+  const pinnedSessionIds = useSessionPinnedStore(React.useCallback(
+    (state) => open || variant === 'sidebar' ? state.ids : EMPTY_PINNED_SESSION_IDS,
+    [open, variant],
+  ));
+  const sessionOrderRanks = useSessionOrderingStore(React.useCallback(
+    (state) => open || variant === 'sidebar' ? state.rankById : EMPTY_SESSION_ORDER_RANKS,
+    [open, variant],
+  ));
   const projects = useProjectsStore((state) => state.projects);
   const activeProjectId = useProjectsStore((state) => state.activeProjectId);
   const currentDirectory = useDirectoryStore((state) => state.currentDirectory);
@@ -691,7 +707,7 @@ export const MobileSessionsSheet: React.FC<MobileSessionsSheetProps> = ({ open,
 
     for (const node of nodes) {
       for (const bucket of node.buckets) {
-        bucket.sessions.sort((a, b) => getSessionTimestamp(b) - getSessionTimestamp(a));
+        bucket.sessions = orderSessionsByLifecycleScopes(bucket.sessions, pinnedSessionIds, sessionOrderRanks);
         for (const session of bucket.sessions) {
           if (!getParentId(session)) node.totalSessions += 1;
         }
@@ -699,7 +715,7 @@ export const MobileSessionsSheet: React.FC<MobileSessionsSheetProps> = ({ open,
     }
 
     return nodes;
-  }, [activeProjectId, projectsMeta, sessions]);
+  }, [activeProjectId, pinnedSessionIds, projectsMeta, sessionOrderRanks, sessions]);
 
   const normalizedDirectory = normalizePath(currentDirectory);
 
@@ -923,14 +939,16 @@ export const MobileSessionsSheet: React.FC<MobileSessionsSheetProps> = ({ open,
   // Flat lists used only by the dedicated search-results view.
   const searchSessionMatches = React.useMemo(() => {
     if (!normalizedQuery) return [] as Session[];
-    return sessions
-      .filter((session) => {
+    return orderSessionsByLifecycleScopes(
+      sessions.filter((session) => {
         const directory = getSessionDirectory(session);
         const project = findExactProjectMatch(projectsMeta, directory);
         return sessionMatchesQuery(session, project?.label ?? '', normalizedQuery);
-      })
-      .sort((a, b) => getSessionTimestamp(b) - getSessionTimestamp(a));
-  }, [normalizedQuery, projectsMeta, sessions]);
+      }),
+      pinnedSessionIds,
+      sessionOrderRanks,
+    );
+  }, [normalizedQuery, pinnedSessionIds, projectsMeta, sessionOrderRanks, sessions]);
 
   const searchProjectMatches = React.useMemo(() => {
     if (!normalizedQuery) return [] as Array<ProjectMeta & { sessionCount: number }>;