bug(unic-archon-dlc): /qa reports failed resolved writes only on the console #664

Problem

After a merge lands, merge in apps/claude-code/unic-archon-dlc/.archon/workflows/unic-dlc-qa.yaml writes the resolved role on every item the pull request links. When some of those writes fail, the run still ends completed, which #652 accepts. But the failed item ids reach only the console line merge: QA for "<slug>" complete …. They are not in merge's structured output and not in any file under <artifacts_dir>/<slug>/.

In AFK nobody reads that line, and uat-prep already notes that console output dies with the worktree. So an item whose resolved write failed stays at ready-for-agent, and a later AFK loop can pick it up again.

Found by review round 1 of PR #663, outside that ticket's scope.

Acceptance criteria

• merge reports, as structured output, the ids of the linked items whose resolved write failed, and reports none when every write succeeded.
• The same list is written to a file under <artifacts_dir>/<slug>/ that outlives the worktree.
• docs/boxes/unic-dlc-qa.md says where an operator finds the list after an AFK run.
• A run where every write succeeded behaves as it does today.