Polish: legible crew roster, End-Scene enforcement, decluttered Hand

- Crew roster bubbles: explicit text color + opaque distinct surface so
  they're legible and stand out from the page in both themes (the bug was
  the <button> defaulting to black-on-dark in dark mode).
- End-Scene enforcement: unless Dev Mode is on, a scene can't end until
  every living Pi-Rat has faced a Deep Challenge or the Obstacle List is
  empty. end_scene_and_transition now returns (ok, msg) and the route
  surfaces a 400; the Deep sees a ✓/○ challenge-progress badge on each
  Pi-Rat bubble. 3 new tests cover the gate.
- Hand panel: dropped the how-to-play blurb and the title in favor of a
  low-profile "Your Hand" label.
- Bump VERSION to 8 with changelog entry; check off TODO.md Polish items.

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

tests/test_game.py

@@ -981,6 +981,53 @@ def test_pvp_challenge(session):
     session.refresh(duel)
     assert duel.status == "succeeded"
 
+def test_end_scene_requires_every_pirat_challenged(session):
+    game, deep, (p2,) = make_scene_game(session)
+    game.dev_mode = False
+    session.add(game)
+    session.commit()
+
+    # Obstacles remain and p2 has not been challenged yet -> blocked.
+    ok, msg = crud.end_scene_and_transition(session, game.id)
+    assert not ok
+    assert p2.name in msg
+    session.refresh(game)
+    assert game.phase == "scene"
+
+    # Once p2 has faced a Deep Challenge, the scene can end.
+    obs = game.obstacles[0]
+    ok, msg = crud.create_challenge(session, game.id, deep.id, p2.id, [obs.id])
+    assert ok, msg
+    ok, msg = crud.end_scene_and_transition(session, game.id)
+    assert ok, msg
+    session.refresh(game)
+    assert game.phase == "between_scenes"
+
+
+def test_end_scene_allowed_when_obstacle_list_empty(session):
+    game, deep, (p2,) = make_scene_game(session)
+    game.dev_mode = False
+    session.add(game)
+    # Clear the Obstacle List; nobody has been challenged.
+    for obs in list(game.obstacles):
+        session.delete(obs)
+    session.commit()
+
+    ok, msg = crud.end_scene_and_transition(session, game.id)
+    assert ok, msg
+    session.refresh(game)
+    assert game.phase == "between_scenes"
+
+
+def test_end_scene_dev_mode_bypasses_challenge_requirement(session):
+    game, deep, (p2,) = make_scene_game(session)
+    assert game.dev_mode  # defaults on for a local checkout
+    ok, msg = crud.end_scene_and_transition(session, game.id)
+    assert ok, msg
+    session.refresh(game)
+    assert game.phase == "between_scenes"
+
+
 def test_obstacles_persist_across_scenes(session):
     game, deep, (p2,) = make_scene_game(session)
     assert len(game.obstacles) == 2