persist sidebar collapsed groups across navigation and restart (#722)

* fix: persist sidebar collapsed groups across navigation and restart

The sidebar's collapsed-group state was stored as local React state in
WorktreeList, so the Sidebar unmount/remount triggered by navigating into
Settings discarded it — returning to the main view re-expanded every
previously collapsed group. Lift the state into the UI slice alongside
groupBy/sortBy/filterRepoIds and persist it via the existing ui:set IPC
so collapse state also survives app restarts.

* fix: clear collapsed groups when switching groupBy mode

Prevents stale keys from accumulating across mode switches and avoids
cross-mode key collisions that could leave groups unexpectedly collapsed.

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Co-authored-by: Jinwoo-H <jinwoo0825@gmail.com>

src/shared/constants.ts

@@ -169,6 +169,7 @@ export function getDefaultUIState(): PersistedUIState {
     sortBy: 'name',
     showActiveOnly: false,
     filterRepoIds: [],
+    collapsedGroups: [],
     uiZoomLevel: 0,
     editorFontZoomLevel: 0,
     worktreeCardProperties: [...DEFAULT_WORKTREE_CARD_PROPERTIES],

src/shared/types.ts

@@ -692,6 +692,7 @@ export type PersistedUIState = {
   sortBy: 'name' | 'smart' | 'recent' | 'repo'
   showActiveOnly: boolean
   filterRepoIds: string[]
+  collapsedGroups: string[]
   uiZoomLevel: number
   editorFontZoomLevel: number
   worktreeCardProperties: WorktreeCardProperty[]