feat(ui): terminal, charts and low-contrast text follow the selected theme

- The lane terminal (xterm) takes its palette from the selected DARK theme —
  it stays dark in light mode, as a terminal should — and repaints live when
  the theme changes (`client/src/lib/terminalTheme.ts`).
- Charts on the Dashboard and Workflows pages draw their grid, axes, labels
  and tooltips from theme tokens instead of hardcoded near-black/white, and
  the activity heatmap ramps from the page surface to the accent, so it reads
  on every theme instead of going near-black on light ones.
- Status/brand text that only worked on dark backgrounds
  (`text-*-300/400`) gets a darker light-mode shade (`text-*-700
  dark:text-*-300`) across sessions, conversations, workflows, config and
  settings. Categorical chart colours are kept.

client/src/components/run/__tests__/TerminalView.test.tsx

@@ -3,11 +3,12 @@
  * @description Tests for the xterm.js-backed terminal view: verifies it opens
  * a WS connection to the right URL, writes incoming binary frames to the
  * mocked terminal, forwards typed input as outgoing binary frames, and
- * re-attaches after the socket drops (server restart) but not after `exit`.
+ * re-attaches after the socket drops (server restart) but not after `exit`,
+ * and recolours live on a dark-theme change without re-attaching.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
-import { render, cleanup } from "@testing-library/react";
+import { render, cleanup, act } from "@testing-library/react";
 import { TerminalView } from "../TerminalView";
 
 const writeMock = vi.fn();
@@ -26,9 +27,13 @@ const termState = {
   rows: 28,
 };
 const onResizeHandlers: Array<() => void> = [];
+const termOptions: { theme?: unknown } = {};
+const ctorArgs: Array<{ theme?: unknown }> = [];
 
 vi.mock("@xterm/xterm", () => ({
-  Terminal: vi.fn().mockImplementation(() => ({
+  Terminal: vi.fn().mockImplementation((opts: { theme?: unknown }) => ({
+    ...(ctorArgs.push(opts), {}),
+    options: termOptions,
     get modes() {
       return termState.modes;
     },
@@ -58,6 +63,10 @@ vi.mock("@xterm/xterm", () => ({
     focus: focusMock,
   })),
 }));
+// jsdom loads no stylesheet, so stand in for the CSS-variable probe.
+vi.mock("../../../lib/terminalTheme", () => ({
+  terminalThemeFor: (id: string) => ({ background: `bg-${id}` }),
+}));
 vi.mock("@xterm/addon-fit", () => ({
   FitAddon: vi.fn().mockImplementation(() => ({ fit: vi.fn() })),
 }));
@@ -103,6 +112,10 @@ describe("TerminalView", () => {
     loadAddonMock.mockClear();
     openMock.mockClear();
     focusMock.mockClear();
+    disposeMock.mockClear();
+    ctorArgs.length = 0;
+    delete termOptions.theme;
+    localStorage.clear();
   });
 
   afterEach(cleanup);
@@ -126,6 +139,21 @@ describe("TerminalView", () => {
     expect(MockWebSocket.instances[0]!.url).toBe("ws://localhost:4820/ws-pty/agenthub-lane-1");
   });
 
+  it("paints the chosen DARK theme and recolours live without re-attaching", () => {
+    localStorage.setItem("theme", "light"); // app in light mode: terminal stays dark
+    localStorage.setItem("agenthub.theme.dark", "apple-dark");
+    render(<TerminalView runId="agenthub-lane-1" wsBaseUrl="ws://localhost:4820" />);
+    expect(ctorArgs[0]!.theme).toEqual({ background: "bg-apple-dark" });
+
+    act(() => {
+      localStorage.setItem("agenthub.theme.dark", "darcula");
+      window.dispatchEvent(new Event("agenthub-theme"));
+    });
+    expect(termOptions.theme).toEqual({ background: "bg-darcula" });
+    expect(MockWebSocket.instances).toHaveLength(1);
+    expect(disposeMock).not.toHaveBeenCalled();
+  });
+
   it("writes incoming WS data to the terminal", () => {
     render(<TerminalView runId="agenthub-lane-1" wsBaseUrl="ws://localhost:4820" />);
     const ws = MockWebSocket.instances[0]!;