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/lanes/LaneCard.tsx

@@ -363,8 +363,8 @@ export function LaneToolsMenu({ lane }: { lane: Lane }) {
           role="menu"
           className="absolute right-0 z-10 mt-1 min-w-44 overflow-hidden rounded-md border border-border-light bg-surface-0 py-1 shadow-lg shadow-black/40"
         >
-          {/* Claude-only: a codex lane has no agents to install. */}
-          {lane.tool !== "codex" && (
+          {/* Claude-only: other CLIs have no agents to install. */}
+          {lane.tool === "claude" && (
             <button
               type="button"
               role="menuitem"
@@ -379,7 +379,7 @@ export function LaneToolsMenu({ lane }: { lane: Lane }) {
               {t("actions.agentsInstall")}
             </button>
           )}
-          {lane.tool !== "codex" && (
+          {lane.tool === "claude" && (
             <button
               type="button"
               role="menuitem"
@@ -487,18 +487,11 @@ export default function LaneCard({
         // renders no frame at all rather than an empty box.
         className="flex flex-col rounded-lg border border-border bg-surface-4 p-2.5 transition-colors hover:border-border-light empty:hidden"
       >
-        {(lane.ci_status || lane.tool === "codex") && (
+        {lane.ci_status && (
           <div className="mb-2 flex flex-wrap items-center gap-1.5 text-[11px]">
-            {lane.ci_status && (
-              <span className="rounded bg-surface-2 px-1.5 py-0.5 text-fg-secondary">
-                CI {lane.ci_status}
-              </span>
-            )}
-            {lane.tool === "codex" && (
-              <span className="rounded border border-border bg-surface-2 px-1.5 py-0.5 text-[10px] text-fg-muted">
-                Codex
-              </span>
-            )}
+            <span className="rounded bg-surface-2 px-1.5 py-0.5 text-fg-secondary">
+              CI {lane.ci_status}
+            </span>
           </div>
         )}