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/i18n/locales/en/lanes.json

@@ -59,6 +59,7 @@
   "addLaneTitlePlaceholder": "Optional",
   "addLaneToolClaude": "Claude Code",
   "addLaneToolCodex": "Codex",
+  "addLaneToolAntigravity": "Antigravity",
   "addLaneToolHint": "Which CLI drives this lane. Cannot be changed later.",
   "addLaneWorktreeDetached": "(detached)",
   "addLaneWorktreesMore": "+{{count}} more",

client/src/i18n/locales/en/run.json

@@ -81,7 +81,7 @@
     "permissionPlan": "plan (read-only planning)",
     "prompt": "Prompt",
     "promptPlaceholder": "Ask Claude anything…",
-    "promptPlaceholderTerminal": "Ask Claude anything…",
+    "promptPlaceholderTerminal": "Ask {{tool}} anything…",
     "sandbox": "Sandbox",
     "sandboxFullAccess": "Full access (dangerous)",
     "sandboxReadOnly": "Read only",

client/src/i18n/locales/vi/lanes.json

@@ -59,6 +59,7 @@
   "addLaneTitlePlaceholder": "Không bắt buộc",
   "addLaneToolClaude": "Claude Code",
   "addLaneToolCodex": "Codex",
+  "addLaneToolAntigravity": "Antigravity",
   "addLaneToolHint": "CLI nào điều khiển lane này. Không thể thay đổi sau này.",
   "addLaneWorktreeDetached": "(detached)",
   "addLaneWorktreesMore": "+{{count}} nữa",

client/src/i18n/locales/vi/run.json

@@ -80,7 +80,7 @@
     "permissionPlan": "plan (chỉ đọc, lập kế hoạch)",
     "prompt": "Prompt",
     "promptPlaceholder": "Hỏi Claude bất cứ điều gì…",
-    "promptPlaceholderTerminal": "Hỏi Claude bất cứ điều gì…",
+    "promptPlaceholderTerminal": "Hỏi {{tool}} bất cứ điều gì…",
     "sandbox": "Sandbox",
     "sandboxFullAccess": "Truy cập đầy đủ (nguy hiểm)",
     "sandboxReadOnly": "Chỉ đọc",