Remove the dead Slay-the-Spire map system (superseded by the lobby)

The lobby hub replaced the between-fights map, leaving the whole map
subsystem unused. Remove it:

- Delete MapScreen.tscn + map_screen.gd (the dead screen) and map_node.gd
  (the MapNode class).
- Strip map generation + navigation from run_state.gd (~90 lines:
  _generate_map/_link_rows/reachable/select_node/node_at/current_node/
  run_complete/complete_current_level, plus map/player_row/col/pending_row/col).
  ensure_run() now guards on a _run_active flag instead of the map array, so
  the shell reloading for each fight still can't wipe the run in progress.
- Simplify active_level() to the lobby flow (override -> lobby -> gate -> arena).
- Drop the now-unread LevelDef.color / is_boss fields and the _make_level args.
- Remove the map test from logic_test.gd.

Live flow unchanged (lobby gates via choose_level, wins via return_to_lobby).
Full headless suite green; menu + shell boot into the lobby clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FBbGXbzg3SD6ZBSadPPF5H

tests/logic_test.gd

@@ -30,7 +30,6 @@ func _run() -> void:
 	test_kick_spread()
 	test_gait_phase_crossing()
 	test_tail_verlet_constraint()
-	test_run_map()
 
 	print("=" .repeat(60))
 	print("Results: %d passed, %d failed" % [_passed, _failed])
@@ -172,60 +171,6 @@ func test_tail_verlet_constraint() -> void:
 	_assert_in_range(damping_factor, 0.85, 1.0, "tail damping factor is reasonable")
 
 
-# ── Run map (Slay-the-Spire progression) ──────────────────────────────────────
-
-func test_run_map() -> void:
-	print("\n-- test_run_map --")
-	var run: Node = root.get_node_or_null("/root/Run")
-	if run == null:
-		_assert_true(false, "Run autoload should exist")
-		return
-
-	run.start_new_run()
-	_assert_true(run.has_run(), "start_new_run builds a map")
-	_assert_true(run.map.size() >= 2, "map has multiple rows")
-
-	# Final row is a single boss node the map funnels toward.
-	var last: Array = run.map[run.map.size() - 1]
-	_assert_eq(last.size(), 1, "final row is a single boss node")
-	_assert_true(last[0].level.is_boss, "final node is a boss level")
-
-	# Connectivity: every node links forward, and every next-row node has a parent.
-	for r: int in run.map.size() - 1:
-		var nxt: Array = run.map[r + 1]
-		var reached := {}
-		for from_node in run.map[r]:
-			_assert_true(from_node.links.size() >= 1, "row %d node links forward" % r)
-			for c: int in from_node.links:
-				_assert_true(c >= 0 and c < nxt.size(), "link column in range")
-				reached[c] = true
-		for c: int in nxt.size():
-			_assert_true(reached.has(c), "row %d col %d has a parent" % [r + 1, c])
-
-	# From the start gate the whole first row is the frontier.
-	_assert_eq(run.reachable().size(), run.map[0].size(), "start frontier is row 0")
-
-	# Advancing follows the chosen node's links.
-	var first = run.map[0][0]
-	run.select_node(first)
-	run.complete_current_level()
-	_assert_eq(run.player_row, 0, "player advanced to row 0")
-	_assert_true(first.cleared, "cleared node is flagged")
-	_assert_eq(run.reachable().size(), first.links.size(),
-		"frontier follows the chosen node's links")
-
-	# Walking to a boss node latches run completion.
-	var guard := 0
-	while not run.run_complete() and guard < 64:
-		var opts: Array = run.reachable()
-		if opts.is_empty():
-			break
-		run.select_node(opts[0])
-		run.complete_current_level()
-		guard += 1
-	_assert_true(run.run_complete(), "reaching a boss node completes the run")
-
-
 # ── Shared helpers ────────────────────────────────────────────────────────────
 
 func _assert_in_range(val: float, lo: float, hi: float, desc: String) -> void: