Task: Scaffold story: Hotfix: default wire codec flip to msgpack breaks ores.qt.headless.tests

(Describe what user-visible-or-internal change this task produces.)

(Implementation strategy. Written when work starts; key decisions are distilled into the parent story's * Decisions at close, but the plan itself stays — it is the historical record of what we did.)

Manual QA scenarios (scaffolded via compass add test_scenario, run through the QA Validation Runner panel) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.

Scaffolded the hotfix story/task pair and wired it into sprint.org's ** Hotfixes section. No code changes ride this task — see the sibling implement task for the actual fix.