A feed row says which map it was, and a generated map's name plays it #417

Split out of #242. The recent-matches feed already selects map (#240) and throws it away. A row should say where it was played, and a generated map should be one click from being played again.

Done looks like

• [ ] Every feed row shows its map name. de_forge is plain text. A gen_… name is a link to /?map=gen_…, built the same way the menu's map link is (src/matchlink.ts / the menu's module from #409). The URL is not built by hand a second time.
• [ ] The name is escaped and validated with src/mapname.ts before it becomes a link. A stored name that does not parse renders as text, never as a link.
• [ ] The row does not get wider on a phone: the name truncates, and the layout does not shift.
• [ ] Tests that would fail without this: a gen_ row carries a link that parses back to the same seed, a de_forge row carries none, and a malformed stored name renders as text.

Files I expect to change

src/pages/game.ts, src/pages/game.test.ts.

Suggested: Vesper, since this is page markup that must not shift.