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/lanes/__tests__/LaneDiffView.test.tsx

@@ -59,6 +59,22 @@ describe("LaneDiffView — side by side", () => {
     expect(screen.getByTestId("lane-diff-split-right").className).toContain("overflow-auto");
   });
 
+  it("keeps an empty filler row one line tall, so the columns stay in step", () => {
+    // Two lines removed, none added: the right column's two rows are fillers.
+    const file = fileWith([
+      { type: "del", oldLine: 1, newLine: null, text: "gone one" },
+      { type: "del", oldLine: 2, newLine: null, text: "gone two" },
+    ]);
+    render(<LaneDiffView file={file} layout="split" />);
+    const fillers = [
+      ...screen
+        .getByTestId("lane-diff-split-right")
+        .querySelectorAll<HTMLElement>("div.flex.w-max"),
+    ];
+    expect(fillers).toHaveLength(2);
+    for (const row of fillers) expect(row.style.minHeight).toBe("16px");
+  });
+
   it("caps a review diff only when it windows; the single-file view fills its parent", () => {
     // Unwindowed, a review-list diff grows so the PANEL is the one vertical
     // scroller (nested 60vh boxes made hunk navigation land nowhere); a
@@ -180,24 +196,40 @@ function rowOf(container: HTMLElement, needle: string): HTMLElement {
 }
 
 describe("LaneDiffView — row styling", () => {
-  it("tints add/del rows with their status fill and left bar; context stays plain", () => {
-    const { container } = render(<LaneDiffView file={ROWS} layout="unified" />);
-    const add = rowOf(container, "x = 2");
-    const del = rowOf(container, "x = 1");
+  // A line added or removed whole: nothing in common with its pair.
+  const WHOLE = fileWith([
+    { type: "ctx", oldLine: 1, newLine: 1, text: "keep()" },
+    { type: "del", oldLine: 2, newLine: null, text: "abc" },
+    { type: "add", oldLine: null, newLine: 2, text: "xyz" },
+  ]);
+
+  it("tints whole-line add/del rows green/red with a left bar; context stays plain", () => {
+    const { container } = render(<LaneDiffView file={WHOLE} layout="unified" />);
+    const add = rowOf(container, "xyz");
+    const del = rowOf(container, "abc");
     const ctx = rowOf(container, "keep()");
     expect(add.className).toContain("bg-status-success/20");
     expect(add.className).toContain("--status-success");
     expect(del.className).toContain("bg-status-danger/20");
     expect(del.className).toContain("--status-danger");
-    expect(ctx.className).not.toMatch(/status-(success|danger)/);
+    expect(ctx.className).not.toMatch(/status-(success|danger)|diff-mod/);
+  });
+
+  it("tints a line edited in place blue on both sides", () => {
+    const { container } = render(<LaneDiffView file={ROWS} layout="unified" />);
+    for (const text of ["x = 1", "x = 2"]) {
+      const row = rowOf(container, text);
+      expect(row.className).toContain("bg-diff-mod/20");
+      expect(row.className).not.toMatch(/status-(success|danger)/);
+    }
   });
 
   it("colours the +/- marker bold in its status colour, context marker muted", () => {
-    const { container } = render(<LaneDiffView file={ROWS} layout="unified" />);
+    const { container } = render(<LaneDiffView file={WHOLE} layout="unified" />);
     const marker = (row: HTMLElement) =>
       row.querySelector<HTMLElement>("span.select-none:not(.w-10)")!;
-    const plus = marker(rowOf(container, "x = 2"));
-    const minus = marker(rowOf(container, "x = 1"));
+    const plus = marker(rowOf(container, "xyz"));
+    const minus = marker(rowOf(container, "abc"));
     const ctx = marker(rowOf(container, "keep()"));
     expect(plus.textContent).toBe("+");
     expect(plus.className).toContain("font-bold");
@@ -210,7 +242,7 @@ describe("LaneDiffView — row styling", () => {
 
   it("emphasises only the changed span of a paired del/add", () => {
     const { container } = render(<LaneDiffView file={ROWS} layout="unified" />);
-    const emph = [...container.querySelectorAll<HTMLElement>("span.bg-fg-primary\\/15")].map(
+    const emph = [...container.querySelectorAll<HTMLElement>("span.bg-diff-mod\\/40")].map(
       (e) => e.textContent
     );
     expect(emph).toEqual(["1", "2"]);
@@ -226,7 +258,7 @@ describe("LaneDiffView — row styling", () => {
         layout="unified"
       />
     );
-    expect(container.querySelector("span.bg-fg-primary\\/15")).toBeNull();
+    expect(container.querySelector("span.bg-diff-mod\\/40")).toBeNull();
   });
 
   it("split view tints each side, and a filler row opposite an unpaired add stays plain", () => {