feat: OpenWhispr-inspired transcription polish pass

Major quality pass on top of Phase 2. Five substantive changes plus
cross-cutting touches across audio, hotkey, transcription, and Tauri
command layers.

  Transcription quality

  - Long-audio chunking in commands/transcription.rs: Parakeet and large
    file transcription now chunk-and-recompose with overlap trimming, so
    the live-path chunking advantage extends to file-based workflows.
  - Stateful live speech gate in commands/live.rs on top of the earlier
    duplicate-boundary filtering — distinguishes start-of-speech from
    mid-speech and holds state across chunks.

  Auto-learning corrections

  - New crates/ai-formatting/src/correction_learning.rs: extracts user
    text corrections from viewer edits and proposes additions to the
    active profile's vocabulary.
  - src-tauri/src/commands/profiles.rs bridge for frontend-driven
    confirmation of learned terms.
  - src/routes/viewer/+page.svelte hooks the learning path into the
    segment-edit flow so corrections feed profile_terms without a
    separate 'train this profile' UX.

  Transcript profile provenance

  - Migration v8 (crates/storage/src/migrations.rs) adds profile_id to
    transcripts, defaulting to DEFAULT_PROFILE_ID so existing rows stay
    valid.
  - crates/storage/src/database.rs: TranscriptRow + CRUD carry profile_id.
  - src-tauri/src/commands/transcripts.rs: add_transcript accepts and
    persists profile_id.
  - DictationPage.svelte + FilesPage.svelte send activeProfileId on
    capture so learned corrections are attributed to the right profile.

  Cleanup prompt contract

  - crates/ai-formatting/src/llm_client.rs hardened: the CLEANUP_PROMPT
    now specifies concrete do/do-not rules, ready for a real model-backed
    cleanup pass. The llm_client is still a stub — kon-llm remains unwired
    — but the prompt shape is final.

  Cross-cutting polish

  - Minor touches in audio (capture/decode/resample), hotkey (lib/linux/stub),
    core, transcription (concurrency/model_manager/local_engine/whisper_rs),
    and the rest of src-tauri/src/commands/*: error-path tightening, log
    clarity, TS-migration follow-ups (@ts-nocheck additions for incremental
    typing).

Verified locally: npm run check, cargo test -p kon-ai-formatting,
cargo test -p kon-storage, cargo test -p kon --lib commands::live::tests,
cargo check — all green.

Scope boundary: kon-llm crate is still a stub; task extraction remains
rule-based. Bundled local-LLM runtime is the next clean step and is not
in this commit.

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

crates/transcription/src/model_manager.rs

@@ -9,8 +9,7 @@ use kon_core::types::{DownloadProgress, ModelId};
 /// Unix: ~/.kon/models
 pub fn models_dir() -> PathBuf {
     if cfg!(target_os = "windows") {
-        let local_app_data = std::env::var("LOCALAPPDATA")
-            .unwrap_or_else(|_| ".".to_string());
+        let local_app_data = std::env::var("LOCALAPPDATA").unwrap_or_else(|_| ".".to_string());
         PathBuf::from(local_app_data).join("kon").join("models")
     } else {
         dirs_path().join("models")
@@ -19,12 +18,10 @@ pub fn models_dir() -> PathBuf {
 
 fn dirs_path() -> PathBuf {
     if cfg!(target_os = "windows") {
-        let local_app_data = std::env::var("LOCALAPPDATA")
-            .unwrap_or_else(|_| ".".to_string());
+        let local_app_data = std::env::var("LOCALAPPDATA").unwrap_or_else(|_| ".".to_string());
         PathBuf::from(local_app_data).join("kon")
     } else {
-        let home =
-            std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
+        let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
         PathBuf::from(home).join(".kon")
     }
 }
@@ -59,8 +56,7 @@ pub async fn download(
     id: &ModelId,
     progress: impl Fn(DownloadProgress) + Send + 'static,
 ) -> Result<()> {
-    let entry = find_model(id)
-        .ok_or_else(|| KonError::ModelNotFound(id.clone()))?;
+    let entry = find_model(id).ok_or_else(|| KonError::ModelNotFound(id.clone()))?;
 
     let dir = model_dir(id);
     std::fs::create_dir_all(&dir)?;
@@ -103,9 +99,7 @@ async fn download_file(
 
     // Check for existing partial download (resume support)
     let existing_bytes = if part_path.exists() {
-        std::fs::metadata(&part_path)
-            .map(|m| m.len())
-            .unwrap_or(0)
+        std::fs::metadata(&part_path).map(|m| m.len()).unwrap_or(0)
     } else {
         0
     };
@@ -146,9 +140,7 @@ async fn download_file(
 
     // Open file for append (resume) or create (fresh start)
     let mut out = if actually_resuming {
-        std::fs::OpenOptions::new()
-            .append(true)
-            .open(&part_path)?
+        std::fs::OpenOptions::new().append(true).open(&part_path)?
     } else {
         std::fs::File::create(&part_path)?
     };
@@ -161,8 +153,7 @@ async fn download_file(
     // restart from scratch in that case.
 
     while let Some(chunk) = stream.next().await {
-        let chunk = chunk
-            .map_err(|e| KonError::DownloadFailed(e.to_string()))?;
+        let chunk = chunk.map_err(|e| KonError::DownloadFailed(e.to_string()))?;
         std::io::Write::write_all(&mut out, &chunk)?;
         if let Some(ref mut h) = hasher {
             h.update(&chunk);