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/e2e/helpers/startup-dsl.ts

@@ -156,14 +156,15 @@ class StartupAssertions {
     this.page = page;
   }
 
-  async expectsSavedHostShell(input: { label: string }): Promise<this> {
+  async expectsSavedHostShell(input: { serverId: string; label: string }): Promise<this> {
     await this.page.getByRole("button", { name: "Open menu", exact: true }).click();
-    await expect(this.page.getByText(input.label, { exact: true })).toBeVisible({
-      timeout: 15_000,
-    });
-    await expect(this.page.getByRole("button", { name: "Add project" })).toBeVisible();
-    await expect(this.page.getByRole("button", { name: "Home" })).toBeVisible();
-    await expect(this.page.getByRole("button", { name: "Settings" })).toBeVisible();
+    await this.page.getByTestId("sidebar-hosts-trigger").click();
+    const hostRow = this.page.getByTestId(`sidebar-host-row-${input.serverId}`);
+    await expect(hostRow).toBeVisible({ timeout: 15_000 });
+    await expect(hostRow).toContainText(input.label);
+    await expect(this.page.getByTestId("sidebar-add-project")).toBeVisible();
+    await expect(this.page.getByTestId("sidebar-home")).toBeVisible();
+    await expect(this.page.getByTestId("sidebar-settings")).toBeVisible();
     await expect(this.page.getByTestId("welcome-screen")).toHaveCount(0);
     return this;
   }