feat(desktop): split cron sessions into their own sidebar section

Scheduler sessions (source=cron) were listed in recents, where their
`[IMPORTANT: …]` first-message previews spammed the list — and because
cron runs are always newest, a burst of them consumed the whole recents
page budget and starved real conversations (sidebar showed 0 sessions).

Recents and cron jobs are now two independent lists:
- Backend: /api/sessions + /api/profiles/sessions accept source /
  exclude_sources; session_count gains exclude_sources. Recents query
  excludes cron; the cron section queries source=cron.
- Desktop: separate $cronSessions store + refreshCronSessions fetch, a
  collapsed (persisted) "Cron jobs" section below Sessions that only
  renders when cron sessions exist, with its own bounded scroller.

apps/desktop/src/store/layout.ts

@@ -22,6 +22,7 @@ export const SIDEBAR_SESSIONS_PAGE_SIZE = 50
 
 const SIDEBAR_PINNED_STORAGE_KEY = 'hermes.desktop.pinnedSessions'
 const SIDEBAR_AGENTS_GROUPED_STORAGE_KEY = 'hermes.desktop.agentsGroupedByWorkspace'
+const SIDEBAR_CRON_OPEN_STORAGE_KEY = 'hermes.desktop.sidebarCronOpen'
 const PANES_FLIPPED_STORAGE_KEY = 'hermes.desktop.panesFlipped'
 
 export const CHAT_SIDEBAR_PANE_ID = 'chat-sidebar'
@@ -54,6 +55,10 @@ export const $sidebarWidth: ReadableAtom<number> = computed($paneStates, states
 export const $pinnedSessionIds = atom(storedStringArray(SIDEBAR_PINNED_STORAGE_KEY))
 export const $sidebarPinsOpen = atom(true)
 export const $sidebarRecentsOpen = atom(true)
+// Cron-job sessions live in their own section below recents, collapsed by
+// default (it only renders at all when cron sessions exist) so the
+// scheduler's `[IMPORTANT: …]` first-message previews don't spam recents.
+export const $sidebarCronOpen = atom(storedBoolean(SIDEBAR_CRON_OPEN_STORAGE_KEY, false))
 export const $sidebarAgentsGrouped = atom(storedBoolean(SIDEBAR_AGENTS_GROUPED_STORAGE_KEY, false))
 // When true, the sessions sidebar moves to the right and the file browser +
 // preview rail move to the left — a mirror of the default layout.
@@ -62,6 +67,7 @@ export const $isSidebarResizing = atom(false)
 export const $sessionsLimit = atom(SIDEBAR_SESSIONS_PAGE_SIZE)
 
 $pinnedSessionIds.subscribe(ids => persistStringArray(SIDEBAR_PINNED_STORAGE_KEY, [...ids]))
+$sidebarCronOpen.subscribe(open => persistBoolean(SIDEBAR_CRON_OPEN_STORAGE_KEY, open))
 $sidebarAgentsGrouped.subscribe(grouped => persistBoolean(SIDEBAR_AGENTS_GROUPED_STORAGE_KEY, grouped))
 $panesFlipped.subscribe(flipped => persistBoolean(PANES_FLIPPED_STORAGE_KEY, flipped))
 
@@ -114,6 +120,10 @@ export function setSidebarRecentsOpen(open: boolean) {
   $sidebarRecentsOpen.set(open)
 }
 
+export function setSidebarCronOpen(open: boolean) {
+  $sidebarCronOpen.set(open)
+}
+
 export function setSidebarAgentsGrouped(grouped: boolean) {
   $sidebarAgentsGrouped.set(grouped)
 }

apps/desktop/src/store/session.ts

@@ -76,6 +76,10 @@ export const $connection = atom<HermesConnection | null>(null)
 export const $gatewayState = atom('idle')
 export const $sessions = atom<SessionInfo[]>([])
 export const $sessionsTotal = atom<number>(0)
+// Cron-job sessions (source === 'cron') are fetched as their own list so the
+// scheduler's always-newest sessions never crowd recents out of the page
+// budget. Powers the collapsed "Cron jobs" sidebar section.
+export const $cronSessions = atom<SessionInfo[]>([])
 // Listable conversation count per profile (children excluded), keyed by profile
 // name. Lets the sidebar scope its "Load more" footer to the active profile so a
 // huge default profile doesn't keep "Load more" visible while browsing a small
@@ -119,6 +123,7 @@ export const setConnection = (next: Updater<HermesConnection | null>) => updateA
 export const setGatewayState = (next: Updater<string>) => updateAtom($gatewayState, next)
 export const setSessions = (next: Updater<SessionInfo[]>) => updateAtom($sessions, next)
 export const setSessionsTotal = (next: Updater<number>) => updateAtom($sessionsTotal, next)
+export const setCronSessions = (next: Updater<SessionInfo[]>) => updateAtom($cronSessions, next)
 export const setSessionProfileTotals = (next: Updater<Record<string, number>>) =>
   updateAtom($sessionProfileTotals, next)
 export const setSessionsLoading = (next: Updater<boolean>) => updateAtom($sessionsLoading, next)