feat(next-up): show the next three deadlines, not one

A reader with two games switched on said the list lost its point at
twenty-one rows and asked for the three closest deadlines up front. One row
was also fragile on its own terms: ticking off the headline event left the
panel pointing at something the reader had no context for.

Three equal panels would be a stat grid, and a reader arrives with one
question — so the shape is one answer at full size and two follow-ups under
it, with no meter, summary or badges to turn the panel into a second copy of
the list below it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/ARCHITECTURE.md

@@ -96,7 +96,7 @@ src/
     sw.js               offline: shell cache, feed fallback
     manifest.webmanifest, icon.svg
     components/
-      NextUp.tsx        the hero countdown          (PRD F1)
+      NextUp.tsx        the next three deadlines    (PRD F2)
       EventRow.tsx      row + meter + caption       (F2, F3)
       Meter.tsx         the depletion meter
       Legend.tsx        what the bars and colours mean