gate: delete the leftover .github/agent/frozen-branches.json (its reader went with #1352) #1371

Owner: Dev

#1352 removed the frozen-branch seal from .github/scripts/enqueue-guard.mjs, but the document it read is still in the tree: .github/agent/frozen-branches.json (blob 12c3f3fe, 69 bytes) —

{
  "branches": ["cursor/"],
  "markers": ["CURSOR_AGENT_PR_BODY"]
}

Nothing reads it any more. On main at 2346077a, enqueue-guard.mjs has no frozen reference at all (grep -i frozen → 0 lines), and enqueue-rules.mjs has none either: the file was the seal's data, and the seal is gone.

Why #1352 could not delete it in the same pull request. enqueue-guard.yml is pull_request_target with ref: main and never runs pull request code, so the judgement of a diff comes from main's copy of the guard. When #1352 first pushed the deletion (8f97e4f5, main still carrying the seal), the check answered:

do not enqueue #1352: frozen: .github/agent/frozen-branches.json is not editable by a pull request

So the reader and the document had to travel apart. #1352 merged at 2346077a; main no longer refuses this edit, and the deletion is now an ordinary T1 change.

Do: one pull request that deletes .github/agent/frozen-branches.json and touches nothing else.