overhaul variant UI: editable card, picker dialog, name editing

[rafavalls]

Summary

Reworks the variants UX end-to-end so page-level and section-level flows share the same components, sizing, and behaviour. Adds a name field on multivariate variants (plumbed through CmsVariant / PageVariantEntry) editable inline from the breadcrumb via a pencil affordance, swaps the custom matcher-picker modal for a CommandDialog list, and rebuilds the rule area as a collapsible bordered card whose open state persists in localStorage. The DateField is now a styled overlay over a real datetime-local input so users can both type and pick — and the overlay finally inherits the same border the input has, fixing the apparent "borderless" look. Both variant lists were unified on a single SortableVariantItem (flag icon only, no colored chip) with drag-reordering on page variants too, and you can now add the first page variant from a flat-sections page or delete a page variant from inside its detail view.

Test plan

• Open a page with no page variants → "Add page variant" creates the multivariate wrapper
• Section + page variant lists look identical (flag icon, drag-reorder, hover dropdown)
• Click pencil on the variant breadcrumb → rename inline; Enter saves, Escape cancels
• Date inputs: click to type, calendar icon to pick, × to clear; border is visible in both focused and unfocused states
• Variant card chevron toggles open/closed; state persists across reloads
• Delete button appears in the page-variant breadcrumb when 2+ variants exist

🤖 Generated with Claude Code

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Summary by cubic

Overhauled the variants UI so page-level and section-level share the same components and flows, with inline variant naming, a new rule picker, and a cleaner date input. Adds drag-reordering for page variants and lets you add the first page variant from a flat page.

• New Features

  • Inline rename for variants from the breadcrumb; stored as a name on multivariate variants and exposed via CmsVariant/PageVariantEntry.
  • Replaced the matcher picker with a searchable CommandDialog.
  • Variant rule area is now a collapsible card whose open state persists in localStorage.
  • Unified lists on SortableVariantItem with drag-reorder for page variants; you can add the first page variant and delete a page variant from its detail view.
  • DateField now overlays a real datetime-local input so users can type or pick, with a clear button and visible border.

• Refactors

  • Consolidated page-level and section-level variant UIs to shared components and sizing; section titles use text-sm, font-semibold.
  • Tools and schemas updated to pass through optional name (getPageSectionsTool, Zod schemas).
  • New handlers: onChangeVariantName, onChangePageVariantName, and onReorderPageVariants; wiring for auto-save and preview refresh included.
  • Simplified rename handlers and removed defensive try/catch around localStorage/showPicker; cleaned up casts now that name is on the types; minor UI tidy-ups.
  • Formatted files and sorted imports to satisfy ci checks.

^{Written for commit 21b1f55. Summary will update on new commits.}