/explore on a phone: the first rows on the first screen, and Make it yours only where it can be made #922

Pillar: P2 Explorer (umbrella #588). Follows #607 (#802) and #606.

Outcome. On a phone (390 px), /explore shows its first rows on the first screen:

• a shorter lead;
• the kind and sort chips in one row;
• the Make it yours button under a row's numbers, not squeezing them.

And a row offers Make it yours only when the viewer may make it theirs. Today a reader sees it on a public repository's private app, which they are refused.

Done means reachable: the page; a test (the button absent where refused, present where allowed); looks at 390 and 1280 on the pull.