[Feature] Add Parakeet V3 engine + fix concurrent downloads

[NOGIT007]

Goal

Add NVIDIA Parakeet V3 engine support alongside Whisper by replacing whisper-rs with transcribe-rs, trimming the Whisper model list to 4 best models, fixing concurrent download crashes, and adding tar.gz extraction for directory-based ONNX models.

Tasks

#	Task	Status
1	Replace whisper-rs with transcribe-rs + add tar/flate2 deps	⌛
2	Update model registry: trim Whisper, add Parakeet V3, new fields	⌛
3	Add download tracking + tar.gz extraction for directory models	⌛
4	Rewrite TranscriptionManager for multi-engine dispatch	⌛
5	Update load_model and transcribe callers for new signatures	⌛
6	Update frontend: Parakeet engine group + extraction UI	⌛

Task Details

Task 1: Replace whisper-rs with transcribe-rs + add tar/flate2 deps

Files:

File	Lines	Change
src-tauri/Cargo.toml	27	Replace whisper-rs with transcribe-rs, add tar + flate2

Verification: cd src-tauri && cargo check

Task 2: Update model registry: trim Whisper, add Parakeet V3, new fields

Files:

File	Lines	Change
src-tauri/src/managers/model.rs	6-15	Remove Moonshine/SenseVoice from EngineType
src-tauri/src/managers/model.rs	20-30	Add download_url, is_directory to ModelInfo, remove repo_id
src-tauri/src/managers/model.rs	57-119	Remove tiny/base, add Parakeet V3 entry, update Whisper URLs
src-tauri/src/managers/model.rs	238-270	Remove get_download_url(), unused helper methods
src-tauri/src/managers/model.rs	272-300	Update list_models_grouped() to include Parakeet

Models after change:

• whisper-small (466MB), whisper-medium (1.5GB), whisper-large-v3-turbo (1.1GB), whisper-large-v3 (1.6GB)
• parakeet-v3 (478MB, int8 ONNX, 25 EU languages)

Verification: cd src-tauri && cargo check

Task 3: Add download tracking + tar.gz extraction for directory models

Files:

File	Lines	Change
src-tauri/src/commands/model.rs	1-10	Add DownloadTrackerState(Arc<Mutex<HashSet<String>>>)
src-tauri/src/commands/model.rs	63-107	Add concurrent guard + is_directory handling
src-tauri/src/commands/model.rs	110-173	Add is_directory param, extraction after download
src-tauri/src/commands/model.rs	new	Add extract_tar_gz() function (flate2 + tar)
src-tauri/src/lib.rs	22	Register DownloadTrackerState

Verification: cd src-tauri && cargo check

Task 4: Rewrite TranscriptionManager for multi-engine dispatch

Files:

File	Lines	Change
src-tauri/src/managers/transcription.rs	1-183	Full rewrite: replace whisper-rs with transcribe-rs LoadedEngine enum

Key changes:

• LoadedEngine enum: Whisper(WhisperEngine) | Parakeet(ParakeetEngine)
• load_model() gains engine_type: EngineType parameter
• transcribe() changes from &self to &mut self
• Whisper uses transcribe_samples with WhisperInferenceParams
• Parakeet uses transcribe_samples with ParakeetInferenceParams { timestamp_granularity: Segment }

Verification: cd src-tauri && cargo check

Task 5: Update load_model and transcribe callers for new signatures

Files:

File	Lines	Change
src-tauri/src/commands/settings.rs	88-106	Get engine_type from ModelManager, pass to load_model()
src-tauri/src/state.rs	264-267	Change let ts to let mut ts for &mut self on transcribe()

Verification: cd src-tauri && cargo check (full clean compile)

Task 6: Update frontend: Parakeet engine group + extraction UI

Files:

File	Lines	Change
src/lib/types.ts	5	Trim EngineType to "whisper" | "parakeet"
src/settings/ModelTab.svelte	28-29	Add extractingModels state, expand parakeet by default
src/settings/ModelTab.svelte	32-72	Add extraction event listeners
src/settings/ModelTab.svelte	275-289	Show "Extracting..." state in model rows
src/settings/ModelTab.svelte	334	Update recommendation text

Verification: bun run build

Research Summary

Files Analyzed

File	Lines	Purpose
src-tauri/Cargo.toml	27	Current whisper-rs dependency
src-tauri/src/managers/model.rs	1-358	Model registry, download URLs, engine types
src-tauri/src/managers/transcription.rs	1-183	Whisper-only transcription via whisper-rs
src-tauri/src/commands/model.rs	1-174	Download command, progress events
src-tauri/src/commands/settings.rs	14-107	load_selected_model() calls tm.load_model()
src-tauri/src/state.rs	225-284	stop_and_transcribe() calls ts.transcribe()
src-tauri/src/lib.rs	1-141	App setup, state registration
src/settings/ModelTab.svelte	1-337	Model browser UI with engine groups
src/lib/types.ts	1-61	TypeScript type definitions

Key Code References

• TranscriptionManager::load_model() at src-tauri/src/managers/transcription.rs:32 — needs engine_type param
• TranscriptionManager::transcribe() at src-tauri/src/managers/transcription.rs:73 — needs &mut self
• load_selected_model() at src-tauri/src/commands/settings.rs:14 — caller of load_model
• stop_and_transcribe() at src-tauri/src/state.rs:225 — caller of transcribe
• download_model() at src-tauri/src/commands/model.rs:63 — needs tracker + extraction
• build_registry() at src-tauri/src/managers/model.rs:57 — model list to update
• Reference: Handy's transcribe-rs usage at /private/tmp/Handy/src-tauri/src/managers/transcription.rs

Risks & Edge Cases

• Risk: transcribe-rs 0.2.5 bundles whisper-rs 0.13.2 (Speech uses 0.15) — Mitigation: transcribe-rs wraps all whisper-rs calls internally; Speech no longer calls whisper-rs directly
• Risk: ONNX Runtime increases binary size by ~40-80MB — Mitigation: acceptable for Parakeet quality gain
• Risk: blob.handy.computer CDN may rate-limit or go down — Mitigation: swap URL to GCP Storage bucket before release
• Risk: Parakeet model extraction takes a few seconds — Mitigation: "Extracting..." UI state with pulse animation
• Risk: Users with whisper-tiny/base selected get fallback on upgrade — Mitigation: existing fallback logic in settings.rs finds first downloaded model

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Branch: feature/parakeet-v3
Tasks: View with ctrl+t

Created with /plan-issue

[NOGIT007]

Completed in v3.2.0 — Parakeet V3 engine added, concurrent download tracking, bigger overlay, GCS model hosting.