Full correctness check against the docs: safer writes, reverts and texts

Safety
- Writes are serialized (Workspace.lock): two background jobs rebuilding one
  package (a sound and its subtitle applied side by side) lost an edit.
- A store copies a bank file or package as "original" only if it matches the
  shipped catalog (Workspace.unoriginal_files: in-memory sounds, bank copies of
  voice lines, subtitles); the editor refuses to switch stores while changes
  are applied. A second store could otherwise resurrect a reverted sound.
- Mod import in the editor asks before overwriting files changed outside the
  tool (it forced silently).
- Revert all in the editor reverts texts too; the uninstaller counts text
  edits before offering to delete the store.
- ackit restore-backup: the full-backup restore decisions.md described; it
  keeps the sounds of WADs without a full copy recorded.
- build_catalog also stops when a subtitle differs from the catalog.

Languages and texts
- Game.language() returns languages without voices (JPN, RUS, ...) and
  Game.voice_archive() their INT voices; ackit text --lang JPN works.
- Menu lookups parse one cached file (find & replace: minutes -> ms).
- Subtitles decode cp1252 as Windows does: the UTF-8-in-cp1252 line
  Speech_TAPE_J_Answer_1_00 (KOR/POL/POR/RUS) is written back byte-for-byte;
  SUB_KOR/SUB_RUS rebuilt from the original game (only those rows changed).
- Mods exported while another language is loaded keep name and line.

Other fixes
- Down-mix folds extra channels in at -3 dB (a 5.1 centre voice was dropped).
- e2e_editor no longer overwrites the user's settings.json; kill_game waits
  for the game to exit before reverts.
- Recorder handles Int32/UInt8 input and split frames; package block cache
  locked; conflict messages, CLI help examples, stale docstrings and doc
  references fixed; tests no longer read this PC's game language.

Docs (decisions, user guide, README, subtitles.md, banks.md, catalog README,
REPORT, NOTES, CLAUDE.md) updated; check_docs: 102 claims match. 148 tests;
e2e_features 9/9, e2e_editor and verify PASS; game original afterwards.

tests/test_codec.py

@@ -59,6 +59,13 @@ def test_audio_helpers():
     assert audio.to_channels(x, 1).shape == (48000, 1)
     assert audio.to_channels(x[:, :1], 6).shape == (48000, 6)
     assert abs(audio.peak_db(audio.normalize(x, -3.0)) + 3.0) < 0.01
+    # down-mix keeps every channel: a voice only in the centre of 5.1 goes to both stereo sides at -3 dB (the
+    # standard fold-down) and to mono at its own level
+    c = np.zeros((100, 6), np.float32)
+    c[:, 2] = 0.5
+    assert np.allclose(audio.to_channels(c, 2), 0.5 * 0.7071) and np.allclose(audio.to_channels(c, 1), 0.5)
+    same = np.repeat(x[:, :1], 2, axis=1)                          # identical L/R: mono = either side, no clipping
+    assert np.allclose(audio.to_channels(same, 1)[:, 0], x[:, 0], atol=1e-6)
     assert audio.trim(x, sr, 0.25, 0.75).shape[0] == 24000
     assert audio.resample(x, 48000, 24000).shape[0] == 24000