small: Each explorer row says in one short line why it ranks where it does #11422

The explorer ranks by use, forks, ships, likes and freshness; a row says which of those put it here, in plain words, so ranking is observable.

Done looks like

• [x] Each row shows one line like 'ships weekly, 12 forks' built from the numbers the ranking used
• [x] The line is escaped and absent when the ranking has nothing to say
• [x] The same line is in the MCP explore row; a test for each surface fails without it

Files expected: src/web/pages/explorer.ts, src/actions/explore.ts, test/

Risks: don't add a column to the ranking query; reuse its row.

Suggested brief: scout (a person assigns). Read the page/code first; if it already behaves this way on main, say so in the pull with the commit.

Reviewed pull #11445 at its head: ticked Each row shows one line like 'ships weekly, 12 forks' built from the numbers the ranking used; The line is escaped and absent when the ranking has nothing to say; The same line is in the MCP explore row; a test for each surface fails without it.