feat(workspace): session view and right panel sit on the page, no cards

The session section and the Files/Changes panel drop their cards; one
vertical divider separates them (none at full width), and the collapsed
rail keeps only that divider. The terminal goes back to the page colour
(--surface-0), and the panel's two sticky bars cover scrolled content in
the page colour instead of the card's.

Inside, the git row loses its bordered box for a bottom divider, and the
ended-session prompt box drops its own fill and shadow.

client/src/lib/__tests__/terminalTheme.test.ts

@@ -24,9 +24,9 @@ const vars: Record<string, string> = {
 describe("buildTerminalTheme", () => {
   it("maps theme tokens onto the xterm palette", () => {
     const t = buildTerminalTheme((n) => vars[n] ?? "");
-    // The card's colour, so the terminal blends into the card it sits on.
-    expect(t.background).toBe("#272a2d");
-    expect(t.cursorAccent).toBe("#272a2d");
+    // The page's colour: the console sits on the page, with no card or frame.
+    expect(t.background).toBe("#111113");
+    expect(t.cursorAccent).toBe("#111113");
     expect(t.foreground).toBe("#edeef0");
     expect(t.cursor).toBe("#edeef0");
     expect(t.selectionBackground).toBe("#43484e");
@@ -60,7 +60,7 @@ describe("buildTerminalTheme", () => {
 describe("terminalThemeFor", () => {
   it("resolves variables on a dark probe scoped to the theme id, then removes it", () => {
     const style = document.createElement("style");
-    style.textContent = `.dark { --surface-3: 1 2 3; } .dark[data-theme="darcula"] { --surface-3: 30 31 32; }`;
+    style.textContent = `.dark { --surface-0: 1 2 3; } .dark[data-theme="darcula"] { --surface-0: 30 31 32; }`;
     document.head.appendChild(style);
     try {
       expect(terminalThemeFor("default").background).toBe("#010203");