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

server/__tests__/git-diff-ops.test.js

@@ -195,6 +195,7 @@ describe("collectChanges — branch range", () => {
 
     const out = await collectChanges(LANE, { range: "branch", base: "development", full: true });
     assert.equal(out.baseRef, "origin/development");
+    assert.equal(out.mergeBase, g(LANE, "merge-base", "origin/development", "HEAD").trim());
     assert.deepEqual(
       out.files.map((f) => f.path),
       ["a.txt"]
@@ -401,6 +402,8 @@ describe("listCommits / readFileAt / listPaths / listTree", () => {
       ["touch keep", "touch a", "init"]
     );
     assert.ok(all[0].refs.includes("HEAD -> feat/thing"));
+    assert.deepEqual(all[0].parents, [all[1].sha]);
+    assert.deepEqual(all[2].parents, []);
 
     const forA = await listCommits(LANE, { file: "a.txt" });
     assert.deepEqual(