Add MTGA Assistant: native Linux deck and game tracker

PySide6 app that follows MTG Arena's Player.log under Steam/Proton and shows
my remaining library with draw odds, my zones, and everything revealed about
the opponent (board, graveyard, exile, known hand/library, seen this match).

- Auto-detects the Steam library, Proton prefix log and MTGA install
- Card names/costs/types from MTGA's local SQLite card database
- Tracks card identity across zone changes, shuffles and Bo3 games
- Scryfall card images with a lazy, size-capped LRU disk cache
- Live log following with restart detection, plus --replay mode
- Flags log gaps where MTGA omits oversized game-state messages

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/mtga_assistant/app.py

@@ -0,0 +1,50 @@
+"""Entry point: mtga-assistant [--log PATH] [--replay PATH [--rate N]]."""
+
+from __future__ import annotations
+
+import argparse
+import sys
+from pathlib import Path
+
+from PySide6.QtWidgets import QApplication
+
+from . import paths
+from .carddb import CardDB
+from .images import ImageCache
+from .ui.main_window import MainWindow
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(description="MTG Arena deck and game tracker")
+    ap.add_argument("--log", type=Path, help="Player.log to follow (default: auto-detect)")
+    ap.add_argument("--replay", type=Path, help="replay a saved log instead of following the live one")
+    ap.add_argument("--rate", type=float, default=40.0, help="replay speed in log events per second")
+    ap.add_argument("--mtga-dir", type=Path, help="MTGA install directory (default: auto-detect)")
+    args, qt_args = ap.parse_known_args()
+
+    cfg = paths.load_config()
+    if args.log:
+        cfg.log_path = args.log
+    if args.mtga_dir:
+        cfg.mtga_dir = args.mtga_dir
+
+    app = QApplication([sys.argv[0], *qt_args])
+    app.setApplicationName("MTGA Assistant")
+    app.setDesktopFileName("mtga-assistant")  # Wayland app_id, usable in Hyprland window rules
+
+    mtga_dir = paths.find_mtga_dir(cfg)
+    db_path = paths.find_card_db(mtga_dir) if mtga_dir else None
+    cards = CardDB(db_path)
+    images = ImageCache(paths.CACHE_DIR, cards, cfg.cache_max_mb * 1024 * 1024)
+
+    if args.replay:
+        win = MainWindow(cards, images, args.replay, replay_rate=args.rate)
+    else:
+        win = MainWindow(cards, images, paths.find_log_path(cfg))
+    app.aboutToQuit.connect(win.shutdown)
+    win.show()
+    return app.exec()
+
+
+if __name__ == "__main__":
+    sys.exit(main())