feat: workspaces own their sessions; desktop parity; sidebar and settings cleanup

Workspace sessions (docs/plans/desktop-parity, phases 1-5 and 7):
- sessions.lane_id: a workspace lists only the sessions its panes held,
  stamped by bindRunSession (first writer wins, nested `claude -p`
  excluded); GET /api/sessions?lane=&archived=
- session row state dot, double-click rename, archive (sessions.archived_at,
  hides only); the activity bar's duplicate Sessions tab removed
- Fork beside Resume (--fork-session, Claude only), Ctrl/Cmd+click a live
  session opens it in a second pane, a diff line's comment is pasted into
  the workspace's last-focused pane (lib/panePaste.ts)

dashboard_runs stability:
- a pane's previous run is archived as <pane>@<started_at> instead of being
  overwritten by INSERT OR REPLACE
- a run is flagged abandoned only once its tmux session is gone, at boot and
  on the run-heal beat (panes outlive a server restart)

UI:
- sidebar: no footer, language or theme block; small collapse button in the
  brand corner; version + update check in the connection details modal, a
  status-bar dot while a release is out; language in Settings -> General
- one Switch component for every switch, the themed Checkbox for every
  checkbox (no native checkboxes)

Also: AI Tools catalog trimmed to 10 built-ins (custom-file prompt modes
tested through fixtures), and the workspace plans under docs/plans/ (the
multi-user server plan lives in the AgentHub-Server repo).

client/src/pages/__tests__/screens.snapshot.test.tsx

@@ -18,7 +18,7 @@ if (nodeProcess) nodeProcess.env.TZ = "UTC";
 
 import { describe, it, expect, vi, beforeEach, afterEach, beforeAll, afterAll } from "vitest";
 import type { ReactNode } from "react";
-import { render, act, screen, fireEvent } from "@testing-library/react";
+import { render, act, screen, fireEvent, within } from "@testing-library/react";
 import { MemoryRouter, Routes, Route } from "react-router-dom";
 import i18n from "i18next";
 
@@ -604,6 +604,29 @@ describe("screen snapshots", () => {
   });
 });
 
+// The language picker moved off the sidebar into Settings → General.
+describe("Settings — language", () => {
+  it("switches the interface language from General", async () => {
+    render(
+      <MemoryRouter initialEntries={["/settings/general"]}>
+        <Settings section="general" />
+      </MemoryRouter>
+    );
+    await settle();
+    const group = screen.getByRole("radiogroup", { name: "Interface language" });
+    expect(within(group).getByRole("radio", { name: "English" })).toHaveAttribute(
+      "aria-checked",
+      "true"
+    );
+    fireEvent.click(within(group).getByRole("radio", { name: "Tiếng Việt" }));
+    await settle();
+    expect(i18n.language).toBe("vi");
+    await act(async () => {
+      await i18n.changeLanguage("en");
+    });
+  });
+});
+
 // Pricing, hook status and CLAUDE_HOME belong to Claude Code (#40 part B):
 // they sit under the Claude Code tab's Overview, not on Dashboard or on the
 // other sub-tabs.