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/LaneConsolePane.tsx

@@ -44,6 +44,7 @@ import type {
   CodexApproval,
 } from "../../lib/api";
 import type { Session, Lane, LaneTool } from "../../lib/types";
+import { LANE_TOOL_LABEL } from "../../lib/types";
 import { TerminalView } from "./TerminalView";
 import { RunSetup } from "./RunSetup";
 import { ActiveRunsSwitcher } from "./RunHistory";
@@ -149,7 +150,7 @@ export function LaneConsolePane({
         : (externalSessions ?? []).filter((s) => s.cwd && owningLaneId(s.cwd, lanes) === laneId),
     [externalSessions, laneId, lanes]
   );
-  const toolLabel = laneTool === "codex" ? "Codex" : "Claude";
+  const toolLabel = LANE_TOOL_LABEL[laneTool];
 
   useEffect(() => {
     onHasActiveRunChange?.(handle !== null);
@@ -568,7 +569,12 @@ export function LaneConsolePane({
       {binaryStatus && !binaryStatus[laneTool]?.found && (
         <div className="rounded-lg border border-status-danger/40 bg-status-danger/10 px-4 py-3 text-sm text-status-danger flex items-center gap-2">
           <AlertCircle className="w-4 h-4 flex-shrink-0" />
-          <span>{t("binary.missing", { cli: laneTool, tool: toolLabel })}</span>
+          <span>
+            {t("binary.missing", {
+              cli: laneTool === "antigravity" ? "agy" : laneTool,
+              tool: toolLabel,
+            })}
+          </span>
         </div>
       )}