Rework slot-mode service selection: pick a section, its services show as a checkbox list, and chosen services collect into a removable 'selected' chip list that persists when switching to another section (services from multiple sections accumulate). Changing the section no longer clears the selection. Add a test covering multi-section accumulation and chip removal. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>