refactor!: rename somafm-tui to beefy-player

The app is now a general internet-radio player rather than a SomaFM client, so the package, console script, MPRIS identity, mpv namespaces, macOS tap names, XDG directories and docs all move to beefy-player.

Environment variables are now BEEFY_* (the old SOMAFM_* spellings are still honoured) and an existing ~/.config/somafm-tui/config.json is migrated on first run, so favourites and volume survive the rename.

The visible interface is untouched: same layout, same logo, same keys.

tests/test_player.py

@@ -5,7 +5,7 @@ import queue
 import time
 from pathlib import Path
 
-from somafm_tui.player import Player
+from beefy_player.player import Player
 
 FAKE_MPV = '''#!/usr/bin/env python3
 import json, os, socket, sys, time
@@ -171,27 +171,27 @@ def test_backend_detection_without_tools(tmp_path, monkeypatch) -> None:
 def test_media_key_messages_become_player_events() -> None:
     player = Player()
     player._handle_mpv_message(
-        {"event": "client-message", "args": ["somafm", "next"]}
+        {"event": "client-message", "args": ["beefy", "next"]}
     )
     event = player.events.get_nowait()
     assert event.kind == "media"
     assert event.detail == "next"
 
     player._handle_mpv_message(
-        {"event": "client-message", "args": ["somafm", "toggle"]}
+        {"event": "client-message", "args": ["beefy", "toggle"]}
     )
     assert player.events.get_nowait().detail == "toggle"
 
     # Foreign namespaces, unknown commands and malformed payloads are ignored.
     player._handle_mpv_message({"event": "client-message", "args": ["other", "next"]})
-    player._handle_mpv_message({"event": "client-message", "args": ["somafm", "seek"]})
+    player._handle_mpv_message({"event": "client-message", "args": ["beefy", "seek"]})
     player._handle_mpv_message({"event": "client-message", "args": None})
     player._handle_mpv_message({"event": "client-message"})
     assert player.events.empty()
 
 
 def test_platform_options_never_leak_to_linux(tmp_path, monkeypatch) -> None:
-    import somafm_tui.player as player_module
+    import beefy_player.player as player_module
 
     monkeypatch.setattr(player_module, "RUNTIME_DIR", tmp_path)
     assert Player()._platform_options("linux") == []
@@ -203,12 +203,12 @@ def test_platform_options_never_leak_to_linux(tmp_path, monkeypatch) -> None:
     assert conf.endswith("mpv-input.conf")
     bindings = (tmp_path / "mpv-input.conf").read_text()
     for line in (
-        "PLAY script-message somafm toggle",
-        "PLAYONLY script-message somafm play",
-        "PAUSEONLY script-message somafm pause",
-        "STOP script-message somafm stop",
-        "NEXT script-message somafm next",
-        "PREV script-message somafm prev",
+        "PLAY script-message beefy toggle",
+        "PLAYONLY script-message beefy play",
+        "PAUSEONLY script-message beefy pause",
+        "STOP script-message beefy stop",
+        "NEXT script-message beefy next",
+        "PREV script-message beefy prev",
     ):
         assert line in bindings