Show host in search results and filter sidebar by multiple hosts (#1825)

* feat(app): show host in command center and multi-select host filter

Command-center agent results now show which host the workspace lives on,
shown only when more than one host is connected (matching the sidebar).

The sidebar display-preferences filter becomes multi-select — pick any
number of hosts instead of one-or-all — and its host rows now carry a
status dot on the left like the other host pickers. Persisted filter
state migrates from the old single host to a host list.

* test(app): extract host-filter and command-center e2e DSL helpers

Move the mechanical menu/search interactions out of the new spec bodies
into focused helpers so the tests read as user intent.

* fix(app): drop the icon from the host filter "All hosts" item

* fix(app): make multi-host e2e seeding order-independent

The offline-host seed relied on Playwright running the test's init script
after the fixture's registry reset — an ordering Playwright does not
guarantee. Write the full registry and set the fixture's disable-once flag,
then reload, so the multi-host seed survives regardless of script order.

Also tag the pre-v2 hostFilter migration reader with COMPAT so the cleanup
sweep can find it.

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

@@ -86,7 +86,7 @@ describe("WorkspaceShortcutTargetsSubscriber", () => {
     });
     useSidebarViewStore.setState({
       groupMode: "project",
-      hostFilter: null,
+      hostFilters: [],
     });
 
     act(() => {
@@ -216,7 +216,7 @@ describe("WorkspaceShortcutTargetsSubscriber", () => {
         );
       useSessionStore.getState().setHasHydratedWorkspaces("host-a", true);
       useSessionStore.getState().setHasHydratedWorkspaces("host-b", true);
-      useSidebarViewStore.getState().setHostFilter("host-b");
+      useSidebarViewStore.getState().toggleHostFilter("host-b");
     });
 
     await act(async () => {