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/components/Sagi/PetMenu.tsx

@@ -7,7 +7,7 @@
  * codex-pets.net for more, and open the Sagi settings. The choice and the size
  * are viewer preferences (`prefs.ts`); the pets themselves live on the server
  * (`server/lib/pets.js`); the list and its actions are `usePets`, shared
- * with Settings → Pet.
+ * with Settings → Appearance.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 

client/src/components/Sagi/Sagi.tsx

@@ -315,7 +315,7 @@ export function Sagi() {
             onClose={() => setMenu(false)}
             onSettings={() => {
               setMenu(false);
-              navigate("/settings/pet");
+              navigate("/settings/appearance#pet");
             }}
           />
         </SagiFlyout>

client/src/components/Sagi/__tests__/Pets.test.tsx

@@ -159,7 +159,7 @@ describe("PetMenu", () => {
     fireEvent.click(screen.getByText("Hide pet"));
     expect(sagiPrefs.getEnabled()).toBe(false);
     // Says where to bring it back.
-    expect(toasts.some((x) => /Settings → Pet/.test(x.message))).toBe(true);
+    expect(toasts.some((x) => /Settings → Appearance/.test(x.message))).toBe(true);
     off();
   });
 

client/src/components/Sagi/usePets.ts

@@ -1,6 +1,6 @@
 /**
  * @file usePets — the pet list and its actions, shared by the mascot's
- * right-click menu (`PetMenu.tsx`) and Settings → Pet (`settings/PetSettings`):
+ * right-click menu (`PetMenu.tsx`) and Settings → Appearance (`settings/PetSettings`):
  * `GET /api/pets`, wearing a pet (a viewer preference, `prefs.ts`), installing
  * a featured pet (downloaded on its first pick), uploading an image or a
  * `.codex-pet.zip` (worn at once), and deleting your own after a confirm