docs(design): drop createSubmitHint from the Known debt entry #105

Follow-up to #88.

Problem #

docs/design.md's Known debt list still says "submitBlockers and createSubmitHint in AutomationForm.css.ts break the field and explanation rules above (#88, #89)." #88 deleted createSubmitHint, so the entry is half stale.

Evidence #

• docs/design.md:107-108.

Expected #

The entry lists only submitBlockers and cites #89.

Acceptance criteria #

• The entry no longer mentions createSubmitHint or #88.