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/tailwind.config.js

@@ -49,6 +49,8 @@ const tinted = {
     danger: tint("--status-danger"),
     warning: tint("--status-warning"),
   },
+  diff: { mod: tint("--diff-mod") },
+  kept: tint("--kept"),
 };
 
 /** @type {import('tailwindcss').Config} */
@@ -104,6 +106,8 @@ export default {
           danger: "rgb(var(--status-danger) / <alpha-value>)",
           warning: "rgb(var(--status-warning) / <alpha-value>)",
         },
+        diff: { mod: "rgb(var(--diff-mod) / <alpha-value>)" },
+        kept: "rgb(var(--kept) / <alpha-value>)",
       },
       backgroundColor: tinted,
       borderColor: tinted,