GuardLane
Which per-thread kill-id field an instrumented script reads. The server lane runs on the Server thread; the client and render lanes BOTH run on the Render thread and share one field (they never run concurrently). Each case names the static field the inlined GETSTATIC reads. A future lane needing its own thread costs one case here, one field, and one branch in TimeoutGuard.setKillId — the rest of the guard state is per-ordinal.