Merge sidebar workspaces across all connected hosts (#1538)

* Merge workspaces across all hosts in the sidebar

Replace per-host sidebar sections with a single merged project list.
Projects that exist on multiple hosts (matched by projectKey) are
collapsed into one row. Host identity is surfaced via:

- A status-only footer pill showing online/offline host counts
- Hover cards with a mandatory host row on every workspace entry
- Subtitles showing the host name when a project spans >1 host
- A host filter in the grouping dropdown (not a sidebar switcher)

Order and group-mode stores migrated from per-server to global keys
with zustand persist migrations. New-workspace screen now shows a
merged project list with a host selector combobox.

Key files:
- workspace-structure.ts: merge algorithm by projectKey
- sidebar-view-store.ts / sidebar-order-store.ts: global state
- sidebar-workspace-list.tsx: context-based subtitle injection
- new-workspace-screen.tsx: host selector in footer row

* Add host filtering to the merged sidebar

The sidebar now merges workspaces from every connected host, so a single
global "active host" no longer fits. Host selection becomes explicit per
action via a host chooser, and agent history pages across all hosts at
once. Removes the active-host / active-server-id model and the
all-agents-list hook that fed it.

* Fix rebase fallout: translate archive host error, update stale workspace-key test

archiveWorkspacesOptimistically used a raw "Host is not connected" string
that the i18n completeness test forbids; route it through i18n.t with the
existing hostDisconnected key. The selectors memoization test asserted
un-prefixed workspace keys, but merged-sidebar keys are serverId-prefixed.

* Fix sidebar review fallout

* Address sidebar review followups

* Fix sidebar workspace identity migration

* Address sidebar review followups

* Handle partial host history failures

* Fix merged sidebar project removal and E2E drift

* Restore history routes and project removal shape

* Remove sidebar host context plumbing

* Tighten sidebar status and host filter state

* Keep new workspace project selection host-compatible

* Migrate sidebar view storage

* Streamline host selection flows

* Update all-host history on archive

* Fix empty project sidebar action

Code regression: the main merge dropped the empty-project New workspace child row while keeping the empty project persistence contract. Restore the row using the project host target so the sidebar stays aligned with the no-host-selection model.

* Fix Japanese shortcut translation key

Stale-base integration: main added the Japanese locale after this branch added cycleAgentMode to the English shortcut help map. Merging main exposed the missing ja key in CI typecheck and resources.test.

* Fix Playwright speech teardown race

packages/app/src/components/workspace-shortcut-targets-subscriber.tsx

@@ -1,9 +1,6 @@
 import { useEffect, useMemo } from "react";
-import {
-  useProjectNamesMap,
-  useStatusModeWorkspaceEntries,
-} from "@/hooks/use-status-mode-workspaces";
 import { useSidebarWorkspacesList } from "@/hooks/use-sidebar-workspaces-list";
+import { useStatusModeWorkspacePlacements } from "@/hooks/use-status-mode-workspaces";
 import { useKeyboardShortcutsStore } from "@/stores/keyboard-shortcuts-store";
 import { useSidebarCollapsedSectionsStore } from "@/stores/sidebar-collapsed-sections-store";
 import { useSidebarViewStore } from "@/stores/sidebar-view-store";
@@ -12,28 +9,16 @@ import {
   buildStatusSidebarShortcutModel,
 } from "@/utils/sidebar-shortcuts";
 
-export function WorkspaceShortcutTargetsSubscriber({
-  enabled,
-  serverId,
-}: {
-  enabled: boolean;
-  serverId: string | null;
-}) {
-  const { projects } = useSidebarWorkspacesList({ serverId, enabled });
-  // groupMode must be resolved before gating the status-mode subscriptions below.
-  const groupMode = useSidebarViewStore((state) =>
-    enabled && serverId ? state.getGroupMode(serverId) : "project",
-  );
-  // Only subscribe to agents/workspaces when the status-group view is actually active.
-  // In project mode (the default), these subscriptions would fire on every agent update
-  // (agents Map identity is replaced on every status transition) with no effect on
-  // the shortcut targets, causing ~15-46 wasted re-renders per agent switch.
+export function WorkspaceShortcutTargetsSubscriber({ enabled }: { enabled: boolean }) {
+  const { workspacePlacements, projects, projectNamesByKey } = useSidebarWorkspacesList({
+    enabled,
+  });
+  const groupMode = useSidebarViewStore((state) => state.groupMode);
   const isStatusMode = enabled && groupMode === "status";
-  const statusWorkspaces = useStatusModeWorkspaceEntries({
-    serverId: isStatusMode ? serverId : null,
-    projects,
+  const statusWorkspacePlacements = useStatusModeWorkspacePlacements({
+    placements: workspacePlacements,
+    enabled: isStatusMode,
   });
-  const projectNamesByKey = useProjectNamesMap(isStatusMode ? serverId : null);
   const collapsedProjectKeys = useSidebarCollapsedSectionsStore(
     (state) => state.collapsedProjectKeys,
   );
@@ -47,7 +32,7 @@ export function WorkspaceShortcutTargetsSubscriber({
   const shortcutModel = useMemo(() => {
     if (groupMode === "status") {
       return buildStatusSidebarShortcutModel({
-        workspaces: statusWorkspaces,
+        workspaces: statusWorkspacePlacements,
         projectNamesByKey,
         collapsedStatusGroupKeys,
       });
@@ -63,17 +48,17 @@ export function WorkspaceShortcutTargetsSubscriber({
     groupMode,
     projectNamesByKey,
     projects,
-    statusWorkspaces,
+    statusWorkspacePlacements,
   ]);
 
   useEffect(() => {
-    if (!enabled || !serverId) {
+    if (!enabled) {
       setSidebarShortcutWorkspaceTargets([]);
       return;
     }
 
     setSidebarShortcutWorkspaceTargets(shortcutModel.shortcutTargets);
-  }, [enabled, serverId, setSidebarShortcutWorkspaceTargets, shortcutModel.shortcutTargets]);
+  }, [enabled, setSidebarShortcutWorkspaceTargets, shortcutModel.shortcutTargets]);
 
   useEffect(() => {
     return () => {