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/LaneStripCard.tsx

@@ -18,6 +18,7 @@
 import { useState } from "react";
 import { useTranslation } from "react-i18next";
 import type { Lane } from "../../lib/types";
+import { LANE_TOOL_LABEL } from "../../lib/types";
 
 const LIVENESS_DOT: Record<Lane["liveness"], string> = {
   active: "bg-status-success",
@@ -115,18 +116,18 @@ export default function LaneStripCard({
         <span className="shrink-0 text-[10px] font-semibold tracking-widest text-fg-muted">
           #{lane.id}
         </span>
-        {/* Codex lanes carry no pipeline, so no stage chip — the Codex tag
-            takes its place. */}
-        {lane.tool === "codex" ? (
+        {/* Only claude lanes carry a pipeline; the others show their CLI's
+            tag in place of the stage chip. */}
+        {lane.tool !== "claude" ? (
           <span className="shrink-0 rounded border border-border bg-surface-2 px-1.5 py-0.5 text-[10px] text-fg-muted">
-            Codex
+            {LANE_TOOL_LABEL[lane.tool]}
           </span>
         ) : (
           <span className="truncate rounded bg-surface-4 px-1.5 py-0.5 text-fg-secondary">
             {lane.stage}
           </span>
         )}
-        {lane.tool !== "codex" && detectionLeads(lane) && (
+        {lane.tool === "claude" && detectionLeads(lane) && (
           <span
             data-testid={`lane-tile-auto-${lane.id}`}
             title={lane.detected_signal || undefined}