Replace a scene's named moments

A cue does NOTHING on its own — it is an ADDRESS, so something else can be told to fire on it.

Today the brand mark reads them: PUT /projects/{id}/branding with formula: "ghost" rests the mark low and lifts it on hit:<name>, which is how a subscribe bump lands on the exact word rather than on a beat.

at is seconds from the scene start, or a moment on the scene's own rulers — word:subscribe, word:#4, bar:3, beat:7, cam:hero, end-2, with +0.25 / +1b / +2B offsets. Prefer the moment form: a cue pinned to a word survives a re-cut of the narration and one pinned to 4.2s does not. It resolves at render against the scene's measured grid, and a cue that does not resolve is dropped rather than firing at zero.

The list is REPLACED, not merged.

curl -X PUT "https://example.com/scenes/497f6eca-6276-4993-bfeb-53cbbbba6f08/cues" \  -H "Content-Type: application/json" \  -d '{    "cues": [      {        "name": "subscribe",        "at": "word:subscribe"      }    ]  }'

{
  "data": {
    "scene_id": "861eef56-1159-4a95-802f-abab2d0cc192",
    "cues": [
      {
        "name": "subscribe",
        "at": "word:subscribe"
      }
    ]
  }
}

{
  "error": {
    "type": "string",
    "code": "string",
    "message": "string"
  }
}

{
  "error": {
    "type": "string",
    "code": "string",
    "message": "string"
  }
}

{
  "error": {
    "type": "string",
    "code": "string",
    "message": "string"
  }
}