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/hooks/sidebar-status-view-model.ts

@@ -1,6 +1,6 @@
-import type { SidebarWorkspaceEntry } from "@/hooks/sidebar-workspaces-view-model";
+import type { SidebarStatusWorkspacePlacement } from "@/hooks/sidebar-workspaces-view-model";
 
-export type StatusBucket = SidebarWorkspaceEntry["statusBucket"];
+export type StatusBucket = SidebarStatusWorkspacePlacement["statusBucket"];
 
 export const STATUS_BUCKET_ORDER: readonly StatusBucket[] = [
   "needs_input",
@@ -21,14 +21,14 @@ export const STATUS_BUCKET_LABELS: Record<StatusBucket, string> = {
 export interface StatusGroup {
   bucket: StatusBucket;
   label: string;
-  rows: SidebarWorkspaceEntry[];
+  rows: SidebarStatusWorkspacePlacement[];
 }
 
 export function buildStatusGroups(
-  workspaces: SidebarWorkspaceEntry[],
+  workspaces: SidebarStatusWorkspacePlacement[],
   projectNamesByKey: Map<string, string>,
 ): StatusGroup[] {
-  const bucketRows = new Map<StatusBucket, SidebarWorkspaceEntry[]>();
+  const bucketRows = new Map<StatusBucket, SidebarStatusWorkspacePlacement[]>();
 
   for (const ws of workspaces) {
     const bucket: StatusBucket = ws.statusBucket;
@@ -54,8 +54,8 @@ export function buildStatusGroups(
 }
 
 function compareStatusRows(
-  a: SidebarWorkspaceEntry,
-  b: SidebarWorkspaceEntry,
+  a: SidebarStatusWorkspacePlacement,
+  b: SidebarStatusWorkspacePlacement,
   projectNamesByKey: Map<string, string>,
 ): number {
   const aTime = a.statusEnteredAt?.getTime() ?? null;