feat: Standard-Dateiname aus Kanal, Titel und Datum des Videos

- yt_untertitel.default_name(): <Kanal>_<Titel>_<Datum>, z. B.
  John_Mearsheimer_Offensive_Realism_Episode_1_Origins_of_the_War_In_Ukraine_2026-07-30
- Bindestriche/Punkte im Wort bleiben, Kanal max. 40, Titel max. 60 Zeichen
  an Wortgrenze; ohne Kanal und Titel die Video-ID
- Gilt ohne -o/-n in extract_text.py (statt output.txt), yt_untertitel.py
  und rede_korrigieren.py -u (statt Video-ID)

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

tests/test_yt_untertitel.py

@@ -12,6 +12,8 @@ URL = "https://www.youtube.com/watch?v=abc123"
 AUTO_ONLY = {
     "id": "abc123",
     "title": "Eine Rede",
+    "channel": "Kanal",
+    "upload_date": "20260328",
     "subtitles": {},
     "automatic_captions": {"de-orig": [], "de": [], "en": []},
 }
@@ -86,6 +88,24 @@ def test_original_language_with_dubbed_audio(info, expected):
     assert yt.original_language(info) == expected
 
 
+@pytest.mark.parametrize("info, expected", [
+    ({"channel": "John Mearsheimer - Offensive Realism",
+      "title": "Episode 1: Origins of the War In Ukraine", "upload_date": "20260730"},
+     "John_Mearsheimer_Offensive_Realism_Episode_1_Origins_of_the_War_In_Ukraine_2026-07-30"),
+    # Title cut at a word boundary after 60 characters; hyphens and dots in words stay
+    ({"channel": "GGBLahnstein", "upload_date": "20260730",
+      "title": "Prof. Gabriele Krone-Schmalz – Respekt geht anders – "
+               "GGB-Gesundheitstage, Lahnstein 28.03.2026"},
+     "GGBLahnstein_Prof_Gabriele_Krone-Schmalz_Respekt_geht_anders_2026-07-30"),
+    ({"uploader": "Ein Kanal", "title": "A/B: Krieg & Frieden 🎤?"}, "Ein_Kanal_A_B_Krieg_Frieden"),
+    ({"title": "Nur Titel", "upload_date": "kaputt"}, "Nur_Titel"),
+    ({"id": "abc123", "title": "🎤 – …"}, "abc123"),
+    ({"title": "x" * 80}, "x" * 60),
+])
+def test_default_name(info, expected):
+    assert yt.default_name(info) == expected
+
+
 def test_available_tracks_hides_dubs():
     assert yt.available_tracks(DUBBED) == (["en-US"], ["en"])
 
@@ -124,13 +144,13 @@ def test_yt_dlp_runs_in_temporary_directory(fake_yt_dlp, tmp_path, monkeypatch):
     assert (tmp_path / "Rede.de-orig.vtt").is_file()
 
 
-def test_main_prefers_manual_and_defaults_to_video_id(fake_yt_dlp, tmp_path, monkeypatch):
+def test_main_prefers_manual_and_default_name(fake_yt_dlp, tmp_path, monkeypatch):
     info = dict(AUTO_ONLY, subtitles={"de": []})
     run = fake_yt_dlp(info)
     monkeypatch.setattr(yt.subprocess, "run", run)
     run_main(monkeypatch, "-u", URL, "-d", tmp_path)
 
-    assert (tmp_path / "abc123.de.vtt").is_file()
+    assert (tmp_path / "Kanal_Eine_Rede_2026-03-28.de.vtt").is_file()
     assert "--write-subs" in run.calls[1]