Refuse a handoff recorded on a finished task card - #2668

Written-by: Dev
Fixes #2667
Owner: Dev
Reviewer: Reviewer

What

A handoff recorded on a finished card no longer reopens it. routeToPool (core/src/host/tasks.js) now refuses accepted / cancelled / failed with stale: A finished task cannot be handed on — the same refusal blockForInput already makes — before it writes queueRole. result-ready is not terminal and still hands on.

The route also answers before the handoff field lands, so a refused write leaves the card exactly as it was, on both entries into writeContract (track_tasks and task-update).

Red first

New test core/test/task-handoff-terminal.test.js, implementation untouched (tip of main d02f292ff7d83464d890892343121b190dae0c18):

$ cd core && TZ=UTC DSH_HARNESS=<harness> node --import ./test/harness-resolve.mjs --test test/task-handoff-terminal.test.js
exit 1
not ok 1 - a finished card keeps its terminal state and refuses the handoff (#2667)
  error: '- task-dbf29eb5ef4b0ec2 [not-started 0% normal] Ship the release note'
ok 2 - a result-ready card still hands on to the next role (#2667)
not ok 3 - failed and cancelled cards refuse a handoff too (#2667)
  error: 'cancelled: - task-f46bc04aa3699451 [not-started 0% normal] Drop the stale note'
# tests 3
# pass 1
# fail 2

The two red lines are the defect: the handoff went through requeue and the card came back open / 0%. The result-ready case was green before and stays green, which is the legal path being guarded.

Ran at this tip: 7f1520c

$ cd core && TZ=UTC DSH_HARNESS=<harness> node --import ./test/harness-resolve.mjs --test \
    test/task-handoff-terminal.test.js test/tasks.test.js test/task-contract.test.js \
    test/bot-tasks.test.js test/task-audit.test.js test/task-handoff-route.test.js \
    test/task-queue-lease.test.js test/group-work.test.js test/board-card.test.js \
    test/room-board.test.js
# tests 108
# pass 108
# fail 0
$ node scripts/ds-bot-patches.mjs check
ok   core/ equals ds-bot/ + patches/ds-bot/
$ node scripts/build-client.mjs --check     # client.js unchanged, check green
$ node .github/scripts/check-mojibake.mjs --check
mojibake: ok — 0 occurrences of U+FFFD
$ node .github/scripts/changelog.mjs check
changelog: 20 fragment(s) in changelog.d/ are well formed
$ cd core && node scripts/lint.mjs
oxlint: 0 errors (87 pre-existing warnings); arch-docs: FAIL — cannot diff against origin/main

Not run

• npm run verify (the whole suite) — the box runs one at a time and another PR fast lane held it.
• node scripts/ds-bot-patches.mjs generate — it requires git, which this box does not have; patches/ds-bot/files/ was updated to the same bytes generate would write, and check passes on the result.
• arch-docs — needs origin/main; no git here. docs/subsystems/core-host.md (the page owning core/src/host/) is updated instead, so CI's run has nothing to object to.
• The smoke test — the change touches src/host/ only in a pure refusal path; no index.js / turn / delivery behaviour changed.

Out of scope

• applyColumn and requeue's other behaviour.
• reworkOf written on an already accepted card (tasks.js openRework path) — reported by the audit scout without a reproduction, not confirmed, not touched here.

Checkpoint

{
"pr": 2668, "claim": "Dev", "issue": 2667,
"summary": "routeToPool now refuses a handoff recorded on an accepted, cancelled or failed card with the same stale refusal blockForInput makes, before queueRole or the handoff field lands, so a finished card keeps its terminal state and claimedBy instead of sliding back to open/0%. result-ready still hands on because that column may return to working. The subsystem page states the rule and a new test covers all four end states plus the legal result-ready path.",
"files": ["core/src/host/tasks.js", "core/test/task-handoff-terminal.test.js", "patches/ds-bot/files/src/host/tasks.js", "docs/subsystems/core-host.md", "changelog.d/2667-task-handoff-terminal.fixed.md"],
"checks": { "ran": "node --test test/task-handoff-terminal.test.js test/tasks.test.js + related task suites; node scripts/ds-bot-patches.mjs check", "result": "green", "at": "7f1520c448f26a3394cf2f643806c685adb4d9fb" },
"next": "none — ready for review (T2: core/src/host, needs a PASS at the tip)"
}