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/navigation/host-runtime-bootstrap.test.ts

@@ -1,6 +1,5 @@
 import { describe, expect, it, vi } from "vitest";
 import {
-  resolveHostIndexRoute,
   resolveStartupBlocker,
   resolveStartupNavigationReady,
   resolveStartupRoute,
@@ -339,14 +338,14 @@ describe("resolveStartupRoute", () => {
     ).toEqual({ kind: "render" });
   });
 
-  it("sends removed host routes to a saved host instead of welcome", () => {
+  it("sends removed host routes to global project selection instead of welcome", () => {
     expect(
       resolveStartupRoute({
         ...baseHostInput,
         route: { kind: "host", serverId: "server-removed" },
         hosts: [{ serverId: "server-next" }],
       }),
-    ).toEqual({ kind: "redirect", href: "/h/server-next/open-project" });
+    ).toEqual({ kind: "redirect", href: "/open-project" });
   });
 
   it("shows welcome from a host route only after the registry proves no hosts exist", () => {
@@ -358,45 +357,3 @@ describe("resolveStartupRoute", () => {
     ).toEqual({ kind: "redirect", href: "/welcome" });
   });
 });
-
-describe("resolveHostIndexRoute", () => {
-  it("restores the remembered workspace when the host index is reopened for the same host", () => {
-    expect(
-      resolveHostIndexRoute({
-        serverId: "server-saved",
-        workspaceSelection: { serverId: "server-saved", workspaceId: "workspace-a" },
-        workspaceSelectionStatus: "exists",
-      }),
-    ).toEqual("/h/server-saved/workspace/workspace-a");
-  });
-
-  it("keeps restoring a remembered workspace before the host workspace list hydrates", () => {
-    expect(
-      resolveHostIndexRoute({
-        serverId: "server-saved",
-        workspaceSelection: { serverId: "server-saved", workspaceId: "workspace-a" },
-        workspaceSelectionStatus: "unknown",
-      }),
-    ).toEqual("/h/server-saved/workspace/workspace-a");
-  });
-
-  it("opens project selection when the remembered workspace is proven missing", () => {
-    expect(
-      resolveHostIndexRoute({
-        serverId: "server-saved",
-        workspaceSelection: { serverId: "server-saved", workspaceId: "workspace-a" },
-        workspaceSelectionStatus: "missing",
-      }),
-    ).toEqual("/h/server-saved/open-project");
-  });
-
-  it("opens project selection when the remembered workspace belongs to another host", () => {
-    expect(
-      resolveHostIndexRoute({
-        serverId: "server-saved",
-        workspaceSelection: { serverId: "server-other", workspaceId: "workspace-a" },
-        workspaceSelectionStatus: "exists",
-      }),
-    ).toEqual("/h/server-saved/open-project");
-  });
-});