[quality] the prefixed label refusal's allowed: none arm (prefixed.ts:251, empty section) is never driven through dist/index.js #419

Finding

The refusal a prefixed label command emits when none of its arguments is in the allowlist has two spellings of the tail, and the bundle suite only ever reaches one:

// src/labels/prefixed.ts:250-252  (requestedLabels)
if (labels.length === 0) {
  throw new Error(`${command.slice(1)}: no allowed value in "${args.join(' ')}"; allowed: ${allowed.join(', ') || 'none'}`)
}

allowed.join(', ') || 'none' falls to 'none' only when the section exists but lists no value. That configuration is accepted: normalizeSection (src/utils/config.ts:438-441, 444-451) takes any array (kind: []) or any mapping with an array values (kind: { values: [], exclusive: true }), so a repository that has stubbed its .prowlabels.yaml sections before filling them refuses every /kind … with allowed: none.

Evidence (main @ 0328961, Node v26, vitest 5.0.3):

• Unit: npx vitest run --coverage → prefixed.ts 100 % lines / branches (__tests__/label/*.test.ts).
• End-to-end: npm run test:coverage:e2e on a scratch branch = origin/main + the heads of all 17 open hold-gated bundle PRs (test(bundle): drive owners-label's early-return and failure arms through dist/index.js #298 … test(bundle): drive react()'s missing comment.id arm (trigger.ts:293) through dist/index.js #413; 61 files / 429 tests pass) → prefixed.ts 100 % lines, 97.22 % branches, uncovered branch 251. The only bundle test of this refusal, __tests__/bundle/prefixedRemoveArms.test.ts:44 (/kind not-allowed), serves the fixture labelFileContentsResp.json whose kind section lists failing-test, cleanup, so the || 'none' fallback never fires.

Unit and e2e evidence are not line-mergeable (#235); they are stated separately.

Recommendation

One PR, one deliverable: a bundle suite __tests__/bundle/prefixedEmptyAllowlist.test.ts that drives through dist/index.js against the fake GitHub:

• /kind cleanup with .prowlabels.yaml = kind: [] → exit 1, error kind: no allowed value in "cleanup"; allowed: none, config reads only (no label read or write)
• /kind cleanup bug with kind: { values: [], exclusive: true } → the same refusal naming both arguments

Priority

• Impact: low
• Effort: low

Filed by quality agent (hold-gated mode)

🐝 Hive Agent: quality | Instance: hosted-available-lke648397-260827-5q9t | SHA: 0328961

— hive: agent=quality backend=copilot model=claude-fable-5.1 copilot=1.0.88