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/sidebar-workspace-list.test.tsx

@@ -152,29 +152,27 @@ function makeHost(): HostProfile {
   };
 }
 
+function setHostProfiles(hosts: HostProfile[]): void {
+  (
+    getHostRuntimeStore() as unknown as {
+      setHostsAndSync: (hosts: HostProfile[]) => void;
+    }
+  ).setHostsAndSync(hosts);
+}
+
 function initializeSidebarState(workspaces: WorkspaceDescriptor[]): void {
   act(() => {
-    getHostRuntimeStore().syncHosts([makeHost()]);
+    setHostProfiles([makeHost()]);
     useSessionStore.getState().initializeSession(SERVER_ID, null as unknown as DaemonClient);
     useSessionStore
       .getState()
       .setWorkspaces(SERVER_ID, new Map(workspaces.map((entry) => [entry.id, entry])));
     useSessionStore.getState().setHasHydratedWorkspaces(SERVER_ID, true);
     useSidebarOrderStore.setState({
-      projectOrderByServerId: {
-        [SERVER_ID]: ["project-a", "project-b"],
-      },
-      workspaceOrderByServerAndProject: {
-        [`${SERVER_ID}::project-a`]: [
-          `${SERVER_ID}:a-main`,
-          `${SERVER_ID}:a-one`,
-          `${SERVER_ID}:a-two`,
-        ],
-        [`${SERVER_ID}::project-b`]: [
-          `${SERVER_ID}:b-main`,
-          `${SERVER_ID}:b-one`,
-          `${SERVER_ID}:b-two`,
-        ],
+      projectOrder: ["project-a", "project-b"],
+      workspaceOrderByProject: {
+        ["project-a"]: [`${SERVER_ID}:a-main`, `${SERVER_ID}:a-one`, `${SERVER_ID}:a-two`],
+        ["project-b"]: [`${SERVER_ID}:b-main`, `${SERVER_ID}:b-one`, `${SERVER_ID}:b-two`],
       },
     });
   });
@@ -258,7 +256,7 @@ function WorkspaceSelectionProbe({
 
 function SidebarFrameProbe({ counts }: { counts: RenderCounts }): ReactElement {
   counts.frame += 1;
-  const { projects } = useSidebarWorkspacesList({ serverId: SERVER_ID });
+  const { projects } = useSidebarWorkspacesList({ hostFilter: SERVER_ID });
 
   return (
     <>
@@ -345,11 +343,11 @@ describe("sidebar workspace render isolation", () => {
     container = null;
     act(() => {
       pathnameState.value = "/";
-      getHostRuntimeStore().syncHosts([]);
+      setHostProfiles([]);
       useSessionStore.getState().clearSession(SERVER_ID);
       useSidebarOrderStore.setState({
-        projectOrderByServerId: {},
-        workspaceOrderByServerAndProject: {},
+        projectOrder: [],
+        workspaceOrderByProject: {},
       });
     });
   });