chore: remove 11 orphan Tauri commands and downstream dead code

Sweep of registered-but-never-invoked commands surfaced by an audit
against the frontend invoke() call sites. Each was confirmed dead via
grep across src-tauri, src, and crates: no caller anywhere.

Removed commands:
- check_model, count_transcripts_command, get_profile_cmd,
  install_update, list_feedback_examples_cmd (utility/CRUD shapes
  never wired)
- save_audio, start_native_capture, stop_native_capture (native-capture
  path superseded by the live transcription session)
- transcribe_pcm, transcribe_pcm_parakeet (PCM commands superseded by
  live session; no frontend caller)
- close_preview_window (preview window is hidden via the
  core:window:allow-hide capability, not the command)

Cascade in audio.rs (~430 lines removed):
- CaptureWorker, NativeCaptureState struct + impl, stop_worker,
  append_recorded_chunk, MAX_NATIVE_CAPTURE_RETURN_SAMPLES,
  persist_audio_samples
- The two cfg(test) tests that exercised stop_worker (the
  recording_filename tests stay, supporting resolve_recording_path
  which the live session uses)

Cascade elsewhere:
- FeedbackDto struct and its From<FeedbackRow> impl
- Stale storage imports in feedback.rs, profiles.rs, transcripts.rs
- tauri::Emitter import in transcription.rs
- app.manage(NativeCaptureState::new()) in lib.rs setup

generate_handler entries removed for all 11 commands. cargo check passes
cleanly with zero warnings; no tests reference any deleted symbols.

Net: 709 deletions, 17 insertions across 9 files.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src-tauri/src/commands/transcripts.rs

@@ -14,11 +14,10 @@
 use serde::{Deserialize, Serialize};
 
 use magnotia_storage::{
-    count_transcripts, delete_transcript as db_delete_transcript,
-    get_transcript as db_get_transcript, insert_transcript as db_insert_transcript,
-    list_transcripts_paged, search_transcripts as db_search_transcripts,
-    update_transcript as db_update_transcript, update_transcript_meta as db_update_transcript_meta,
-    InsertTranscriptParams, TranscriptRow,
+    delete_transcript as db_delete_transcript, get_transcript as db_get_transcript,
+    insert_transcript as db_insert_transcript, list_transcripts_paged,
+    search_transcripts as db_search_transcripts, update_transcript as db_update_transcript,
+    update_transcript_meta as db_update_transcript_meta, InsertTranscriptParams, TranscriptRow,
 };
 
 use crate::AppState;
@@ -145,14 +144,6 @@ pub async fn list_transcripts(
         .map_err(|e| e.to_string())
 }
 
-/// Total count of transcripts (for "showing X of N" UI).
-#[tauri::command]
-pub async fn count_transcripts_command(state: tauri::State<'_, AppState>) -> Result<i64, String> {
-    count_transcripts(&state.db)
-        .await
-        .map_err(|e| e.to_string())
-}
-
 #[tauri::command]
 pub async fn get_transcript(
     state: tauri::State<'_, AppState>,