Declutter the challenge panel and obstacle titles (v4)

Per playtest feedback:
- Drop the per-challenge 'Plays:' line — redundant with the card column and the
  event log (also removes the now-unused chPlays const).
- Drop the 'Attempted by … drag a card … assist' how-to paragraph; players know
  the basics, and the challenge header already names who's challenged.
- Replace the 'Red/Black Obstacle · match to draw' tag with the original card in
  the title (e.g. '5♣ — Loitering Mermaid'), and color the title by suit. The
  left border already marks color; the dead .obstacle-color-tag CSS is removed.

Suit glyphs in the title use plain text symbols (not SUIT_EMOJI) so they take
the theme-aware suit color and stay readable on the dark panel. Verified in
light and dark.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/changelog.js

@@ -6,10 +6,17 @@
 //   - Add a CHANGELOG entry only when a commit changes something players can
 //     see. Skip refactors, tests, and tooling. Keep wording player-facing.
 
-export const VERSION = 3;
+export const VERSION = 4;
 
 // Newest first. Each entry: { version, date: 'YYYY-MM-DD', changes: [string, ...] }.
 export const CHANGELOG = [
+    {
+        version: 4,
+        date: '2026-06-15',
+        changes: [
+            'Tidied the Challenge panel: dropped the redundant “Plays” list and the how-to-play blurb. Each Obstacle now leads with its card (e.g. “K♦”) in the title, colored by suit.',
+        ],
+    },
     {
         version: 3,
         date: '2026-06-15',