feat: edit in the Changes panel, git graph history, plan quota (v2.3.0)

- Changes panel: a working file opens in a CodeMirror editor with its diff
  inline (DiffEditor.tsx, @codemirror/merge, lazy-loaded); Changes folds the
  unchanged lines, Whole file shows them; side by side at 50/50 and full
  width; a Revert per block; original from HEAD or the branch's merge base
  (`mergeBase` on GET /git/changes?range=branch)
- Every diff: green = line added whole, red = removed whole, blue = edited
  in place (--diff-mod)
- History drawn as a commit graph (#58: `parents` on GET /git/log,
  --date-order; lib/commitGraph.ts)
- Per-workspace never-stage list, drawn orange in the Files tree (--kept);
  closed Terminal rows past three deleted
- Status bar plan quota for Claude (per account) and Codex
  (GET /api/pricing/quota, server/lib/quota.js); compact hover panel that
  stays open, Refresh button with a spinner
- Settings → Appearance holds language, theme and pet; Ctrl+Shift+C copies;
  compact sidebar navigation and short session times

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, within } from "@testing-library/react";
+import { render, act, screen, fireEvent } from "@testing-library/react";
 import { MemoryRouter, Routes, Route } from "react-router-dom";
 import i18n from "i18next";
 
@@ -593,13 +593,9 @@ describe("screen snapshots", () => {
   it("Run", async () => {
     await snapshot(<Workspace />, "/run");
   });
-  it("Settings", async () => {
-    await snapshot(<Settings />, "/settings");
-  });
   it("Settings — notifications", async () => {
     await snapshot(<Settings section="notifications" />, "/settings/notifications");
   });
-  // General split into General / Data / About: keep the moved content covered.
   it("Settings — data", async () => {
     await snapshot(<Settings section="data" />, "/settings/data");
   });
@@ -611,29 +607,6 @@ 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.