[MWPW-205910] Single featured-product tile spans full grid width

[rea16068]

A single CSS rule so a lone featured-product tile spans the full grid width instead of sitting in one half of the 2-column grid.

Change

.featured-products-list > *:only-child { grid-column: 1 / -1; }

Targets the direct grid child (<li class="featured-product">), matching the grid's repeat(2, 1fr) column structure.

Resolves: MWPW-205910

Test plan

• CSS lint: clean (npx stylelint 'event-libs/v1/c2/blocks/event-*/**/*.css')
• No unit test possible — WTR doesn't load block CSS, so computed grid-column isn't observable in tests.
• Visual verification needed — requesting reviewer confirm the single-tile layout, since I can't preview from a fork branch.

[rea16068]

Closing in favor of #305 — opened from a direct branch on adobecom/event-libs now that I have write access, which also allows proper visual preview via the eventlibs param, Milestone, and Labels.