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/lib/api.ts

@@ -390,6 +390,7 @@ import type {
   CodexHooksStatus,
   AntigravityHooksStatus,
   CostResult,
+  ToolQuota,
   DashboardEvent,
   Lane,
   LaneChangeRange,
@@ -1392,6 +1393,11 @@ export const api = {
       applyScope(qs);
       return request<CostResult>(`/pricing/cost?${qs.toString()}`);
     },
+    /** GET /api/pricing/quota - plan quota spent per native tool; `force` for a Refresh. */
+    quota: (force = false) =>
+      request<{ tools: ToolQuota[]; checkedAt: string }>(
+        `/pricing/quota${force ? "?force=1" : ""}`
+      ),
     /**
      * GET /api/pricing/cost/:sessionId - cost for one session, priced as of
      * the session's start date.