phsl / new-api

- Add mobile filter-button placeholder in skeleton when `isMobile` is true
- Plumb `isMobile` from `PricingVendorIntroWithSkeleton` to `PricingVendorIntroSkeleton`
- Rename skeleton key from 'button' to 'copy-button' for consistency
- Neutralize copy-button skeleton color to match input (use neutral palette)
- Keep “Total x models” tag inline with title on mobile; wrap only when space is insufficient
- Mirror the same title+tag layout in the skeleton (flex-row flex-wrap items-center)
- No linter errors introduced

Affected files:
- web/src/components/table/model-pricing/layout/header/PricingVendorIntro.jsx
- web/src/components/table/model-pricing/layout/header/PricingVendorIntroSkeleton.jsx
- web/src/components/table/model-pricing/layout/header/PricingVendorIntroWithSkeleton.jsx