Requires:

{"heatFrames": 15}

Exit condition:

"leaveWithRunway": {
  "length": 7,
  "openEnd": 1
}

Unlocks doors:

{"types": ["ammo"], "requires": []}

Dev note: The blocks respawn, so no need to split this in two runways. While waiting for respawn would take additional heat frames, the spawner makes that more or less inconsequential.