tests: cover the roster and the command line

The roster tests pin down the .old backup rotation and the five minute
periodic save, with a fake clock in place of datetime.

The command line tests call main() in-process with the save and data
paths in a temporary directory, so coverage counts them. They cover
listing, loading, importing and exporting saves, dumping and loading
word lists, and the first-run character creation. The curses UI is
swapped for a stub there so a stray code path fails instead of taking
over the terminal.

--load-save 0 falls through to the menu and --load-save -1 plays the
last character instead of being rejected; both are marked xfail.

A shared fixture restores pytest's SIGINT handler after the UIs
install their own.

tests/saves.py

@@ -0,0 +1,43 @@
+"""Characters, rosters and .pqw files for the UI and CLI tests."""
+
+from pathlib import Path
+
+from test_pqw import played
+
+from pqcli import pqw
+from pqcli.game_data import load_game_data
+from pqcli.mechanic import Player
+from pqcli.roster import Roster
+
+DATA = load_game_data()
+
+
+def hero(name: str = "Exportée", ticks: int = 300) -> Player:
+    """A character that has played for a while."""
+    player = played(ticks).player
+    player.name = name
+    return player
+
+
+def save_path(config: Path) -> Path:
+    """Where pqcli keeps its roster with XDG_CONFIG_HOME set to config."""
+    return config / "pqcli" / "save.dat"
+
+
+def write_roster(config: Path, *players: Player) -> Path:
+    path = save_path(config)
+    Roster(path, list(players)).save()
+    return path
+
+
+def read_names(config: Path) -> list[str]:
+    return [player.name for player in Roster.load(save_path(config)).players]
+
+
+def write_pqw(path: Path, player: Player, *, online: bool = False) -> Path:
+    """Write player as a .pqw; online adds fields the import warns about."""
+    game = pqw.export_game(player, DATA)
+    if online:
+        game["online"] = {"realm": "Alpaquil", "passkey": 1}
+    path.write_text(pqw.encode(game), encoding="ascii")
+    return path