Treat language selection as meeting language

PROJECT_KNOWLEDGE.md

@@ -1,5 +1,14 @@
 # Project Knowledge
 
+## Meeting language
+
+The GUI's `meeting_language` is passed through `MeetingDetails.language` to both
+Meeting Context `meeting.language` and `MvpMeetingConfig.language` (Whisper).
+Meeting Lab derives explicit protocol output language from the persisted context,
+also during regeneration, and records derived `output_language` provenance in
+protocol runtime metadata. Missing context language defaults to German. There is
+no separate protocol-language setting or automatic context/transcript translation.
+
 ## Vision
 
 Meeting Assistant turns recorded meetings into reviewed, user-facing protocols

README.md

@@ -23,6 +23,13 @@ reference recorder, but imported audio is not tied to OBS-specific behavior.
 
 ## Processing Pipeline
 
+The existing **Meeting language** selector controls both transcription and protocol
+output: `de` means German for both, and `en` means English for both. The selection
+is saved in Meeting Context (`meeting.language`) and reused for protocol-only
+regeneration without retranscription. Older contexts without a language retain
+German protocol output. Names, speaker mappings and authored Meeting Context are
+preserved; no transcript translation stage is added.
+
 ```text
 Audio file
     -> FFmpeg preparation (mono, 16 kHz PCM WAV; normalization optional)

src/mka/ui/streamlit_app.py

@@ -458,7 +458,10 @@ def main() -> None:
     description = st.text_area("Description / context", height=100, key="meeting_description")
     metadata_columns = st.columns(3)
     language = metadata_columns[0].selectbox(
-        "Meeting language", options=["de", "en"], key="meeting_language"
+        "Meeting language",
+        options=["de", "en"],
+        key="meeting_language",
+        help="Language for both transcription and the generated protocol.",
     )
     has_date = metadata_columns[1].checkbox(
         "Meeting date is known", value=True, key="meeting_has_date"

tests/test_meeting_service.py

@@ -323,19 +323,28 @@ def test_build_context_translates_mentioned_only_person(tmp_path: Path) -> None:
     ]
 
 
+@pytest.mark.parametrize("language", ["de", "en"])
 def test_process_translates_configuration_and_disables_diarization(
     tmp_path: Path,
+    language: str,
 ) -> None:
     service, gateway = make_service(tmp_path)
     audio = tmp_path / "meeting.wav"
     audio.write_bytes(b"audio")
 
     outcome = service.process(
-        audio, meeting(), participants(), ProcessingOptions(diarization_enabled=False)
+        audio,
+        replace(meeting(), language=language),
+        participants(),
+        ProcessingOptions(diarization_enabled=False),
     )
 
     assert outcome.succeeded
     assert gateway.config_values is not None
+    assert gateway.config_values["language"] == language
+    assert service.build_context(replace(meeting(), language=language), participants()).data[
+        "meeting"
+    ]["language"] == language
     assert gateway.config_values["diarization"] == "off"
     assert gateway.config_values["model"] == "test:model"
     assert gateway.config_values["protocol_num_ctx"] == 32_768