feat(lanes): Antigravity lanes, release exited panes, fresh Codex starts

- antigravity: a third lane tool running Antigravity's `agy` CLI. `-i`
  carries the first prompt, `--continue` resumes; `agy` has no model,
  effort or permission flag, and `--dangerously-skip-permissions` is never
  emitted. No pipeline, no agents install, and no AI Router (native only,
  else EUNSUPPORTED). Add lane gains an Antigravity choice and the binary
  probe maps it to `agy`.
- UI: the lane card no longer renders a frame holding only a "Codex" chip,
  and the prompt box names the lane's CLI ("Ask Codex anything…"), via
  LANE_TOOL_LABEL.
- runs: a pane that exits is released on a 10 s server beat
  (healAllRunIds, DASHBOARD_RUN_HEAL_MS). Codex and Antigravity fire no
  hook, so their lanes stayed "running" until something re-read them.
- codex: Start no longer sends resumeLast — only "Resume last session"
  continues the previous thread.

client/src/components/run/__tests__/RunSetup.test.tsx

@@ -380,7 +380,7 @@ describe("RunSetup — per-tool fields", () => {
 });
 
 describe("RunSetup — / and @ suggestions in the prompt box", () => {
-  const box = () => screen.getByPlaceholderText(i18n.t("run:fields.promptPlaceholderTerminal"));
+  const box = () => screen.getByPlaceholderText(/ anything…$/);
 
   it("lists the lane's commands, skills and the CLI built-ins on /, and Enter picks one", async () => {
     const { spies } = renderSetup({ prompt: "" });
@@ -423,3 +423,26 @@ describe("RunSetup — / and @ suggestions in the prompt box", () => {
     expect(api.ccConfig.commands).not.toHaveBeenCalled();
   });
 });
+
+describe("RunSetup — antigravity lanes", () => {
+  it("names the lane's CLI in the prompt box and drops the flags `agy` lacks", () => {
+    const { spies } = renderSetup({ tool: "antigravity", model: "opus", effort: "high" });
+    expect(screen.getByPlaceholderText("Ask Antigravity anything…")).toBeTruthy();
+    expect(screen.queryByText(i18n.t("run:fields.model"))).toBeNull();
+    expect(screen.queryByText(i18n.t("run:fields.effort"))).toBeNull();
+
+    fireEvent.click(screen.getByText(i18n.t("run:actions.start")));
+    expect(spies.onStart).toHaveBeenCalledWith(
+      expect.objectContaining({ model: undefined, effort: undefined, permissionMode: undefined })
+    );
+  });
+});
+
+describe("RunSetup — codex lanes", () => {
+  it("starts a fresh codex run instead of resuming the last one", () => {
+    const { spies } = renderSetup({ tool: "codex" });
+    fireEvent.click(screen.getByText(i18n.t("run:actions.start")));
+    expect(spies.onStart).toHaveBeenCalledOnce();
+    expect(spies.onStart.mock.calls[0][0].resumeLast).toBeUndefined();
+  });
+});