feat(desktop): reload a tab from its right-click menu

Right-click any tab and pick Reload: the pane's content remounts in
place — effects re-run, state resets, measurements are retaken — while
the tab keeps its slot and every other tab is untouched.

A per-pane epoch atom keys the contribution inside the zone body, so
reload never rewrites the layout tree. Both tab menus offer it: the
zone strip menu (tool panels, the file tree, a fresh draft's main tab)
and the session tab menu (tiles + the loaded main tab).

apps/desktop/src/app/chat/sidebar/session-actions-menu.tsx

@@ -7,6 +7,7 @@ import {
   closeAllTreeTabs,
   closeOtherTreeTabs,
   closeTreeTabsToRight,
+  reloadTreePane,
   treeTabCloseTargets
 } from '@/components/pane-shell/tree/store'
 import {
@@ -239,12 +240,24 @@ function useSessionActions({
     })
   ]
 
-  // TAB — close verbs that act on the strip (tabs only; a row isn't a tab).
+  // TAB — verbs that act on the strip (tabs only; a row isn't a tab).
   const closeTargets = surface === 'tab' && tabPaneId ? treeTabCloseTargets(tabPaneId) : null
 
-  const tabCloseItems: ActionItemSpec[] =
+  const tabItems: ActionItemSpec[] =
     surface === 'tab'
       ? [
+          ...(tabPaneId
+            ? [
+                spec({
+                  icon: 'refresh',
+                  label: t.zones.reload,
+                  onSelect: () => {
+                    triggerHaptic('selection')
+                    reloadTreePane(tabPaneId)
+                  }
+                })
+              ]
+            : []),
           ...(onClose
             ? [
                 spec({
@@ -342,10 +355,10 @@ function useSessionActions({
       />
       <kit.Separator />
       {workItems.map(item => renderActionItem(kit, item))}
-      {tabCloseItems.length > 0 && (
+      {tabItems.length > 0 && (
         <>
           <kit.Separator />
-          {tabCloseItems.map(item => renderActionItem(kit, item))}
+          {tabItems.map(item => renderActionItem(kit, item))}
         </>
       )}
       <kit.Separator />

apps/desktop/src/components/pane-shell/tree/pane-reload.test.ts

@@ -0,0 +1,28 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+// Right-click a tab -> Reload remounts THAT pane's content: its epoch (the
+// React key the zone renderer hands the contribution) advances, and no other
+// pane's does. The layout tree itself must never move.
+
+describe('reloadTreePane', () => {
+  beforeEach(() => {
+    window.localStorage.clear()
+    vi.resetModules()
+  })
+
+  it('advances only the reloaded pane epoch and leaves the tree alone', async () => {
+    const tree = await import('@/components/pane-shell/tree/store')
+    const model = await import('@/components/pane-shell/tree/model')
+
+    tree.declareDefaultTree(model.group(['workspace', 'files'], { active: 'workspace', id: 'grp-main' }))
+
+    const before = tree.$layoutTree.get()
+
+    tree.reloadTreePane('workspace')
+    tree.reloadTreePane('workspace')
+
+    expect(tree.$treePaneEpochs.get().workspace).toBe(2)
+    expect(tree.$treePaneEpochs.get().files).toBeUndefined()
+    expect(tree.$layoutTree.get()).toBe(before)
+  })
+})

apps/desktop/src/components/pane-shell/tree/renderer/tree-group.tsx

@@ -33,6 +33,7 @@ import {
   $newSessionTabAction,
   $panesWithCloser,
   $treeDragging,
+  $treePaneEpochs,
   activateTreePane,
   closeAllTreeTabs,
   closeOtherTreeTabs,
@@ -42,6 +43,7 @@ import {
   isCollapsePane,
   isSessionStripPane,
   noteActiveTreeGroup,
+  reloadTreePane,
   restoreTreePane,
   SESSION_TILE_DRAG,
   setTreeGroupHeaderHidden,
@@ -96,6 +98,12 @@ function ZoneMenu({
 
     return (
       <>
+        {renderActionItem(kit, {
+          icon: 'refresh',
+          label: t.zones.reload,
+          onSelect: () => reloadTreePane(targetPane())
+        })}
+        <kit.Separator />
         {paneId !== undefined &&
           renderActionItem(kit, {
             icon: 'close',
@@ -178,6 +186,9 @@ export function TreeGroup({
   const narrow = useStore($narrowViewport)
   const newSessionTabAction = useStore($newSessionTabAction)
   const panesWithCloser = useStore($panesWithCloser)
+  // Reload epochs: only an explicit tab-menu Reload writes here, so this
+  // subscription costs nothing on a normal render.
+  const paneEpochs = useStore($treePaneEpochs)
 
   const paneFor = (id: string) => panes.find(p => p.id === id)
 
@@ -557,9 +568,14 @@ export function TreeGroup({
                     // can gate its hot (per-token) subscriptions while hidden;
                     // the group id identifies the ZONE it lives in, for state
                     // that is per-zone rather than per-tab (composer pop-out).
+                    // The reload epoch keys the CONTENT, not this layer: a
+                    // Reload remounts the contribution (effects re-run, state
+                    // resets) while the layer — and every other tab — stays.
                     <PaneGroupContext.Provider value={node.id}>
                       <PaneVisibleContext.Provider value={isActive}>
-                        <ContribBoundary id={pane.id}>{pane.render()}</ContribBoundary>
+                        <ContribBoundary id={pane.id} key={paneEpochs[paneId] ?? 0}>
+                          {pane.render()}
+                        </ContribBoundary>
                       </PaneVisibleContext.Provider>
                     </PaneGroupContext.Provider>
                   ) : (

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

@@ -450,6 +450,22 @@ export function treeTabCloseTargets(paneId: string): { all: number; others: numb
   return { all: others.length + (isUncloseablePane(paneId) ? 0 : 1), others: others.length, right: right.length }
 }
 
+/**
+ * RELOAD — a pane's remount counter, the tab menu's Reload (browser parity:
+ * right-click a tab, reload what's in it). The zone renderer keys a pane's
+ * body layer on its epoch, so bumping it unmounts the contribution and mounts
+ * it fresh — data effects re-run, measurements are retaken — while the layout
+ * tree, the tab's position, and every other tab stay exactly as they were.
+ * Absent until a pane is first reloaded (no key churn on a normal boot).
+ */
+export const $treePaneEpochs = atom<Readonly<Record<string, number>>>({})
+
+export function reloadTreePane(paneId: string): void {
+  const epochs = $treePaneEpochs.get()
+
+  $treePaneEpochs.set({ ...epochs, [paneId]: (epochs[paneId] ?? 0) + 1 })
+}
+
 /** Close a tab the way its kind expects: a tool panel leaves the strip (and
  *  syncs its toggle), everything else routes through its owning Close. */
 export function closeTabPane(paneId: string) {

apps/desktop/src/i18n/ar.ts

@@ -2236,6 +2236,7 @@ export const ar = defineLocale({
     closeRunningBody:
       'هذه المحادثة ما زالت تعمل (أو تنتظر إدخالك). إغلاق التبويب يخفيها فقط — ستحتفظ الجلسة بتقدمها ويمكن إعادة فتحها من الشريط الجانبي.',
     closeRunningConfirm: 'إغلاق التبويب',
+    reload: 'إعادة التحميل',
     closeOthers: 'إغلاق الأخرى',
     closeToRight: 'إغلاق ما على اليمين',
     closeAll: 'إغلاق الكل',

apps/desktop/src/i18n/en.ts

@@ -2663,6 +2663,7 @@ export const en: Translations = {
     closeRunningBody:
       'This chat is still working (or waiting on your input). Closing the tab hides it — the session keeps its progress and can be reopened from the sidebar.',
     closeRunningConfirm: 'Close tab',
+    reload: 'Reload',
     closeOthers: 'Close others',
     closeToRight: 'Close to the right',
     closeAll: 'Close all',

apps/desktop/src/i18n/ja.ts

@@ -2489,6 +2489,7 @@ export const ja = defineLocale({
     hideHeader: 'ヘッダーを隠す',
     minimize: '最小化',
     restore: '復元',
+    reload: '再読み込み',
     closeOthers: '他を閉じる',
     closeToRight: '右側を閉じる',
     closeAll: 'すべて閉じる',

apps/desktop/src/i18n/types.ts

@@ -2262,6 +2262,7 @@ export interface Translations {
     closeRunningTitle: string
     closeRunningBody: string
     closeRunningConfirm: string
+    reload: string
     closeOthers: string
     closeToRight: string
     closeAll: string

apps/desktop/src/i18n/zh-hant.ts

@@ -2409,6 +2409,7 @@ export const zhHant = defineLocale({
     hideHeader: '隱藏標題列',
     minimize: '最小化',
     restore: '還原',
+    reload: '重新載入',
     closeOthers: '關閉其他',
     closeToRight: '關閉右側',
     closeAll: '全部關閉',

apps/desktop/src/i18n/zh.ts

@@ -2841,6 +2841,7 @@ export const zh: Translations = {
     closeRunningTitle: '关闭正在运行的标签？',
     closeRunningBody: '此对话仍在运行（或正在等待你的输入）。关闭标签只会隐藏它——会话将保留进度，可从侧边栏重新打开。',
     closeRunningConfirm: '关闭标签',
+    reload: '重新加载',
     closeOthers: '关闭其他',
     closeToRight: '关闭右侧',
     closeAll: '全部关闭',