[larspohlmann]

Closes #2053

What

#2037 (#2036) replaced the magazine's whole duplicates footer with "x more sources" mini cards. The redesign was meant only for a Trending story's other outlets. A post that appears in several feeds lost its "Also in" pills.

• app-more-sources, the footer slot every magazine block renders, now chooses between two footers:
  • a story: the mini cards, unchanged;
  • any other entry with duplicates: <app-entry-duplicates>, exactly as before feat(#2036): magazine "x more sources" footer that opens into mini cards #2037 ("Also in" pills, a popover with the copy's row).
• The pill footer only exists on a card that has copies.
• The story footer stretches across a kicker card (align-self: stretch). The kicker card's align-items: flex-start shrank its grid to the content.
• docs/design-language.md now says which entries get which footer.

The pills are untouched. In a kicker card their top rule still ends at their content width, as it did before #2037.

Testing

• npm run check is green: 476 suites, 6357 tests.
• more-sources spec: a non-story duplicate renders the "Also in" pills and no mini cards; a story renders mini cards and no pills.
• The hero spec's pre-feat(#2036): magazine "x more sources" footer that opens into mini cards #2037 test (duplicate copy, pill, then popover, then open) is restored, next to a story test through the mini card.
• The Trending Playwright smoke passes in both layouts.
• Live check on :4200: a stubbed duplicated post in the magazine shows "Also in" with two pills.