This third slice of #241 adds stable question and option IDs, canonical decision-record validation, and shared-draft operations for appending options, suggestions, retitling, and reopening. Selected answers retain option IDs alongside their readable labels; existing persisted custom answers still derive correctly. Duplicate option IDs are refused without changing existing draft selections.

The existing keyed “Add an option” path stays in use. It is adapted to the wider stored definition type, with its persistence and retry tests retained. Canonical records remain a separate module until the later runtime layer connects them to the document and durable sidecar.

**Review scope:** 33 files; +876/−74 source lines and +1,173/−5 test lines. Merge after the replay layer. This introduces no new route or automatic Save behavior.

**Validation:** 137 focused question, record, Store, existing service, and agent-tool tests pass (515 assertions); full workspace/E2E types, repository CI, and formatting pass.