fix(desktop): keep pinned + recent sessions visible across compression

Long-running sessions auto-compress: the gateway ends the original session
and surfaces the live continuation under a new id (list_sessions_rich projects
the root forward to its tip). Two symptoms fell out of the id rotation:

- A pinned session "vanished" — the pin is stored as the pre-compression root
  id, but the sidebar only matched on the live id, so it was filtered out.
  Pins now resolve on the durable lineage-root id (`_lineage_root_id`, already
  surfaced by the projection): the sidebar indexes sessions by both ids, pin/
  unpin and reorder operate on the durable id, and `sessionPinId()` is shared
  with the Cmd+P toggle. Existing pins keep working with no migration.

- A freshly-continued session was missing from the list until you ungrouped +
  "load 50 more" — the list paginated by original start time, so an old-but-
  active conversation sat past the first page. The desktop now requests
  `order=recent` (GET /api/sessions gains an `order` param backed by the
  existing recency CTE), surfacing live continuations on the first page.

apps/desktop/src/app/chat/sidebar/index.tsx

@@ -54,7 +54,8 @@ import {
   $sessions,
   $sessionsLoading,
   $sessionsTotal,
-  $workingSessionIds
+  $workingSessionIds,
+  sessionPinId
 } from '@/store/session'
 
 import { type AppView, ARTIFACTS_ROUTE, MESSAGING_ROUTE, SKILLS_ROUTE } from '../../routes'
@@ -73,7 +74,12 @@ const SIDEBAR_NAV: SidebarNavItem[] = [
     icon: props => <Codicon name="robot" {...props} />,
     action: 'new-session'
   },
-  { id: 'skills', label: 'Skills & Tools', icon: props => <Codicon name="symbol-misc" {...props} />, route: SKILLS_ROUTE },
+  {
+    id: 'skills',
+    label: 'Skills & Tools',
+    icon: props => <Codicon name="symbol-misc" {...props} />,
+    route: SKILLS_ROUTE
+  },
   { id: 'messaging', label: 'Messaging', icon: props => <Codicon name="comment" {...props} />, route: MESSAGING_ROUTE },
   { id: 'artifacts', label: 'Artifacts', icon: props => <Codicon name="files" {...props} />, route: ARTIFACTS_ROUTE }
 ]
@@ -189,24 +195,45 @@ export function ChatSidebar({
 
   const sortedSessions = useMemo(() => [...sessions].sort((a, b) => sessionTime(b) - sessionTime(a)), [sessions])
 
-  const sessionsById = useMemo(() => new Map(sessions.map(s => [s.id, s])), [sessions])
   const workingSessionIdSet = useMemo(() => new Set(workingSessionIds), [workingSessionIds])
 
-  const visiblePinnedIds = useMemo(
-    () => pinnedSessionIds.filter(id => sessionsById.has(id)),
-    [pinnedSessionIds, sessionsById]
-  )
+  // Index sessions by both their live id and their lineage-root id so a pin
+  // stored as the pre-compression root resolves to the live continuation tip.
+  const sessionByAnyId = useMemo(() => {
+    const map = new Map<string, SessionInfo>()
 
-  const visiblePinnedIdSet = useMemo(() => new Set(visiblePinnedIds), [visiblePinnedIds])
+    for (const s of sessions) {
+      map.set(s.id, s)
 
-  const pinnedSessions = useMemo(
-    () => visiblePinnedIds.map(id => sessionsById.get(id)!).filter(Boolean),
-    [visiblePinnedIds, sessionsById]
-  )
+      if (s._lineage_root_id && !map.has(s._lineage_root_id)) {
+        map.set(s._lineage_root_id, s)
+      }
+    }
+
+    return map
+  }, [sessions])
+
+  const pinnedSessions = useMemo(() => {
+    const seen = new Set<string>()
+    const out: SessionInfo[] = []
+
+    for (const pinId of pinnedSessionIds) {
+      const session = sessionByAnyId.get(pinId)
+
+      if (session && !seen.has(session.id)) {
+        seen.add(session.id)
+        out.push(session)
+      }
+    }
+
+    return out
+  }, [pinnedSessionIds, sessionByAnyId])
+
+  const pinnedRealIdSet = useMemo(() => new Set(pinnedSessions.map(s => s.id)), [pinnedSessions])
 
   const unpinnedAgentSessions = useMemo(
-    () => sortedSessions.filter(s => !visiblePinnedIdSet.has(s.id)),
-    [sortedSessions, visiblePinnedIdSet]
+    () => sortedSessions.filter(s => !pinnedRealIdSet.has(s.id)),
+    [sortedSessions, pinnedRealIdSet]
   )
 
   const agentSessions = useMemo(
@@ -236,7 +263,10 @@ export function ChatSidebar({
       return
     }
 
-    reorderPinnedSession(String(active.id), newIndex)
+    // Sortable ids are live session ids; the pinned store is keyed by durable
+    // (lineage-root) ids, so translate before reordering.
+    const dragged = sessionByAnyId.get(String(active.id))
+    reorderPinnedSession(dragged ? sessionPinId(dragged) : String(active.id), newIndex)
   }
 
   const handleAgentDragEnd = ({ active, over }: DragEndEvent) => {
@@ -536,7 +566,7 @@ function SidebarSessionsSection({
       isWorking: workingSessionIdSet.has(session.id),
       onArchive: () => onArchiveSession(session.id),
       onDelete: () => onDeleteSession(session.id),
-      onPin: () => onTogglePin(session.id),
+      onPin: () => onTogglePin(sessionPinId(session)),
       onResume: () => onResumeSession(session.id),
       session
     }

apps/desktop/src/app/chat/sidebar/virtual-session-list.tsx

@@ -5,6 +5,7 @@ import { type FC, useCallback, useMemo, useRef } from 'react'
 
 import type { SessionInfo } from '@/hermes'
 import { cn } from '@/lib/utils'
+import { sessionPinId } from '@/store/session'
 
 import { SidebarSessionRow } from './session-row'
 
@@ -77,7 +78,7 @@ export const VirtualSessionList: FC<VirtualSessionListProps> = ({
       isWorking: workingSessionIdSet.has(session.id),
       onArchive: () => onArchiveSession(session.id),
       onDelete: () => onDeleteSession(session.id),
-      onPin: () => onTogglePin(session.id),
+      onPin: () => onTogglePin(sessionPinId(session)),
       onResume: () => onResumeSession(session.id)
     }
 

apps/desktop/src/app/desktop-controller.tsx

@@ -32,6 +32,8 @@ import {
   $freshDraftReady,
   $gatewayState,
   $selectedStoredSessionId,
+  $sessions,
+  sessionPinId,
   setAwaitingResponse,
   setBusy,
   setCurrentBranch,
@@ -224,10 +226,14 @@ export function DesktopController() {
       return
     }
 
-    if ($pinnedSessionIds.get().includes(sessionId)) {
-      unpinSession(sessionId)
+    // Pin on the durable lineage-root id so the pin survives auto-compression.
+    const session = $sessions.get().find(s => s.id === sessionId || s._lineage_root_id === sessionId)
+    const pinId = session ? sessionPinId(session) : sessionId
+
+    if ($pinnedSessionIds.get().includes(pinId)) {
+      unpinSession(pinId)
     } else {
-      pinSession(sessionId)
+      pinSession(pinId)
     }
   }, [])