phase.add appended the entry after the 999.x backlog (the decimal backlog
convention confused the auto-placement). Moved it into Phase Details before
## Progress, added it to the top checklist + Progress table + execution order,
gave it goal/success-criteria/candidate-scope (promotes backlog 999.2/3/6/7/8/9),
renamed the dir to 06-ux-polish, and bumped STATE to 6 phases (50%).
