fix(desktop): layout reset reopens collapsed sidebars

resetLayoutTree() claims to "restore everything" but never reopened collapsed
SIDES. A sidebar hidden before a reset survived it, so the next ⌘B toggled from
that stale-hidden state into a SHOW — and the user's hide never persisted across
reload. Reopen every bound side through its store so the toggles stay truthful.

Adds a store-level regression test (real modules, re-import = reload) covering
hide→reload and the reset→hide→reload repro.

apps/desktop/src/components/pane-shell/tree/store.ts

@@ -1148,6 +1148,14 @@ export function resetLayoutTree() {
   resetHandlers.forEach(fn => fn())
   // Everything still missing (plugin panes) adopts by placement.
   adoptContributedPanes()
+
+  // "Restore everything" includes collapsed SIDES: reopen every bound side
+  // (through its store, so $sidebarOpen / the toggles stay truthful). Without
+  // this a sidebar hidden before the reset silently survives it, flipping the
+  // next ⌘B into a SHOW — so hiding never appears to persist.
+  for (const side of Object.keys(sideOpeners) as TreeSide[]) {
+    sideOpeners[side]?.(true)
+  }
 }
 
 // Dev hook for automation.

apps/desktop/src/store/sidebar-collapse-persistence.test.ts

@@ -0,0 +1,64 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+// Ground-truth repro for "hiding the sidebar doesn't persist on reload": drive
+// the REAL stores, then re-import them (fresh module state reading persisted
+// localStorage) to simulate a ⌃R reload. `bind` mirrors the controller wiring.
+async function loadStores() {
+  const layout = await import('./layout')
+  const tree = await import('@/components/pane-shell/tree/store')
+
+  return {
+    layout,
+    tree,
+    bind: () => tree.bindTreeSideVisibility('left', layout.$sidebarOpen, layout.setSidebarOpen),
+    leftCollapsed: () => tree.$collapsedTreeSides.get().has('left')
+  }
+}
+
+const reload = () => vi.resetModules() // fresh modules; localStorage is the carry-over
+
+describe('sidebar collapse persistence', () => {
+  beforeEach(() => {
+    window.localStorage.clear()
+    vi.resetModules()
+  })
+
+  it('restores a hidden sidebar after a reload', async () => {
+    const s1 = await loadStores()
+    s1.bind()
+    s1.layout.setSidebarOpen(false)
+    expect(s1.leftCollapsed()).toBe(true)
+
+    reload()
+    const s2 = await loadStores()
+    expect(s2.layout.$sidebarOpen.get()).toBe(false) // persisted open:false survives
+    s2.bind()
+    expect(s2.leftCollapsed()).toBe(true) // and re-collapses
+  })
+
+  // The reported repro: a sidebar HIDDEN before a reset must be reopened by the
+  // reset ("restore everything"); otherwise the stale-hidden state flips the
+  // next ⌘B into a SHOW, and the user's hide never persists.
+  it('reset reopens a hidden sidebar, so a later hide persists across reload', async () => {
+    const s1 = await loadStores()
+    const { group, split } = await import('@/components/pane-shell/tree/model')
+    s1.tree.declareDefaultTree(split('row', [group(['sessions']), group(['workspace'])], [1, 3]))
+    s1.bind()
+
+    s1.layout.setSidebarOpen(false) // hidden BEFORE the reset
+    expect(s1.leftCollapsed()).toBe(true)
+
+    s1.tree.resetLayoutTree() // ⌘⇧ reset — restores everything, sidebar shown again
+    expect(s1.layout.$sidebarOpen.get()).toBe(true)
+    expect(s1.leftCollapsed()).toBe(false)
+
+    s1.layout.toggleSidebarOpen() // ⌘B now genuinely hides
+    expect(s1.layout.$sidebarOpen.get()).toBe(false)
+
+    reload()
+    const s2 = await loadStores()
+    expect(s2.layout.$sidebarOpen.get()).toBe(false)
+    s2.bind()
+    expect(s2.leftCollapsed()).toBe(true)
+  })
+})