feat(transcription): Phase A — engine protocol + registry + orchestrator (clean-room)

Introduces the architectural spine for the Wyrdnote engine layer per
the spec at outputs/wyrdnote/2026-05-10-engine-architecture-spec.md
in the CORBEL-Main workspace, Codex-reviewed 2026/05/10.

Clean-room derivative of VoiceInk's TranscriptionService /
TranscriptionServiceRegistry / TranscriptionPipeline shape. Built from
the architectural pattern only; no GPL-3.0 code, comments, or
identifiers lifted. Wyrdnote names, control flow, and trait signatures
are original.

What this lands:

crates/cloud-providers/src/provider.rs (new, 184 lines)
  TranscriptionProvider async trait. Object-safe via async_trait so
  Arc<dyn TranscriptionProvider> is the canonical shape. Lives in
  cloud-providers (not transcription) per D7 so an OEM licensee
  implementing the trait depends only on this crate plus magnotia-core
  (no transcription internals leaked through the trait surface).
  Surrounding types: ProviderId (lower-kebab-case), ProviderKind,
  NetworkRequirement, CostClass, ProviderCapabilities, EngineProfile,
  ProviderTranscript. Compile-time object-safety witness in tests.

crates/cloud-providers/Cargo.toml (modified)
  Adds async-trait + serde dependencies.

crates/cloud-providers/src/lib.rs (modified)
  Re-exports the provider surface.

crates/transcription/src/registry.rs (new, 183 lines)
  EngineRegistry: catalogue of providers keyed by ProviderId. Push-style
  registration, default-provider id captured at construction. Read-only
  after boot. Full unit-test coverage: empty default, register/get
  round-trip, default-resolves-after-registration, re-register replaces,
  ids enumeration.

crates/transcription/src/orchestrator.rs (new, 286 lines)
  LocalProviderAdapter wraps Arc<LocalEngine>, presents async
  TranscriptionProvider upward via tokio::task::spawn_blocking. Per D7
  the adapter lives in the orchestrator, NOT as impl TranscriptionProvider
  for LocalEngine — this keeps the dependency edge one-directional and
  avoids leaking async-runtime requirements onto the synchronous
  Transcriber trait.

  Orchestrator: single transcribe() entry point; resolves a provider
  from the registry, derives TranscriptionOptions from the EngineProfile,
  dispatches. Returns a clear error when an unregistered provider is
  named. Unit tests use a mock CannedProvider to validate dispatch,
  error handling, and option routing without booting a real model.

crates/transcription/Cargo.toml (modified)
  Depends on magnotia-cloud-providers + async-trait. Dev-dep tokio
  gains macros + rt-multi-thread features for #[tokio::test].

crates/transcription/src/lib.rs (modified)
  Exports Orchestrator, EngineRegistry, LocalProviderAdapter, and
  re-exports the provider trait surface so downstream crates depend
  only on magnotia-transcription for both local engines and the trait.

KNOWN-ISSUES.md (modified)
  Adds KI-06: existing dictation, live, and meeting commands still call
  LocalEngine::transcribe_sync directly via pick_engine. The orchestrator
  path is dormant until a Phase A.1 follow-up commit migrates the call
  sites. Cloud providers (Phase G) cannot be exercised end-to-end until
  the rewire lands. Phasing rationale: this commit lands the abstractions
  cleanly with full test coverage; the rewire is a separate diff so the
  chunking + post-processing logic in transcribe_file moves without
  inflating this commit beyond review fidelity.

Test results: 9 new tests pass (orchestrator: dispatches, errors-on-
unregistered, routes-initial-prompt, object-safe; registry: empty-default,
round-trip, default-resolves, re-register, ids-list). Pre-existing
59 transcription tests + 5 cloud-providers tests still green.
cargo check --workspace clean.

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

crates/cloud-providers/src/lib.rs

@@ -1,3 +1,8 @@
 pub mod keystore;
+pub mod provider;
 
 pub use keystore::{retrieve_api_key, store_api_key};
+pub use provider::{
+    CostClass, EngineProfile, NetworkRequirement, ProviderCapabilities, ProviderId, ProviderKind,
+    ProviderTranscript, TranscriptionProvider,
+};

crates/cloud-providers/src/provider.rs

@@ -0,0 +1,184 @@
+//! `TranscriptionProvider` is the async-native trait every transcription
+//! backend implements, regardless of whether the work happens locally
+//! (Whisper, Parakeet, Moonshine via the `LocalProviderAdapter` in
+//! `magnotia-transcription`) or remotely (OpenAI Whisper, Groq,
+//! Deepgram, etc.).
+//!
+//! Living in `magnotia-cloud-providers` is deliberate: the AGPL OEM
+//! exception (≥£2k/yr) requires a clean trait surface that an OEM
+//! licensee can implement without depending on Wyrdnote's transcription
+//! internals. The trait crate stays small; provider implementations
+//! sit alongside.
+//!
+//! Object-safety discipline: no generic methods, no `Self`-returning
+//! methods. The compile-time witness in `tests` enforces this.
+
+use std::fmt;
+
+use async_trait::async_trait;
+use magnotia_core::error::Result;
+use magnotia_core::types::{AudioSamples, ModelId, Transcript, TranscriptionOptions};
+use serde::{Deserialize, Serialize};
+
+/// Stable, lower-kebab-case identifier for a provider. Used in user
+/// profiles, settings storage, and logs. Examples: `local-whisper`,
+/// `local-parakeet`, `openai-whisper`, `groq-whisper-v3`.
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub struct ProviderId(String);
+
+impl ProviderId {
+    pub fn new(id: impl Into<String>) -> Self {
+        Self(id.into())
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+}
+
+impl fmt::Display for ProviderId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+/// Whether a provider runs locally or over the network. The orchestrator
+/// inspects this to decide whether to honour an offline-only profile.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum ProviderKind {
+    Local,
+    Cloud(NetworkRequirement),
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum NetworkRequirement {
+    /// Provider requires a live network connection on every call.
+    Online,
+    /// Provider can fall back to a cached or queued path when offline.
+    OnlineWithFallback,
+}
+
+/// Indicative cost class for UI surfacing. Not a billing source of truth.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum CostClass {
+    /// No marginal cost beyond the user's local hardware.
+    Free,
+    /// Per-call cost; user supplies their own API key (BYOK).
+    PaidByok,
+    /// Per-call cost; provider billed by CORBEL on the user's behalf.
+    PaidManaged,
+}
+
+/// Capabilities a provider advertises to the orchestrator and the UI.
+/// Superset of `magnotia_transcription::TranscriberCapabilities` for
+/// local providers, with extra fields cloud providers populate.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub struct ProviderCapabilities {
+    pub sample_rate: u32,
+    pub channels: u16,
+    pub initial_prompt_supported: bool,
+    pub language_hint_supported: bool,
+    pub streaming_supported: bool,
+    pub cost_class: CostClass,
+}
+
+/// User-selectable engine configuration. The orchestrator resolves
+/// `engine_id` against the `EngineRegistry`, then derives
+/// `TranscriptionOptions` from the remaining fields.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EngineProfile {
+    pub engine_id: ProviderId,
+    pub model_id: Option<ModelId>,
+    pub language: Option<String>,
+    pub initial_prompt: Option<String>,
+}
+
+impl EngineProfile {
+    pub fn new(engine_id: ProviderId) -> Self {
+        Self {
+            engine_id,
+            model_id: None,
+            language: None,
+            initial_prompt: None,
+        }
+    }
+
+    pub fn to_options(&self) -> TranscriptionOptions {
+        TranscriptionOptions {
+            language: self.language.clone(),
+            initial_prompt: self.initial_prompt.clone(),
+        }
+    }
+}
+
+/// Result returned by `TranscriptionProvider::transcribe`. Carries the
+/// transcript plus inference timing so the orchestrator can surface
+/// latency without losing it across the trait boundary.
+#[derive(Debug, Clone)]
+pub struct ProviderTranscript {
+    pub transcript: Transcript,
+    pub inference_ms: u64,
+}
+
+/// Async-native unified interface for transcription providers.
+///
+/// `Send + Sync` supertraits: providers live in an `Arc<dyn
+/// TranscriptionProvider>` shared across tokio tasks. `async_trait`
+/// macro converts the async methods into boxed futures so the trait
+/// stays object-safe.
+#[async_trait]
+pub trait TranscriptionProvider: Send + Sync {
+    fn provider_id(&self) -> ProviderId;
+
+    fn kind(&self) -> ProviderKind;
+
+    fn capabilities(&self) -> ProviderCapabilities;
+
+    /// Idempotent pre-flight. Local providers verify the model is
+    /// loaded into memory; cloud providers validate credentials and
+    /// reach the endpoint. Called before the first `transcribe` of a
+    /// session, and again after a profile or settings change that
+    /// invalidates the previous prepare.
+    async fn prepare(&self, profile: &EngineProfile) -> Result<()>;
+
+    /// Transcribe a chunk of audio. The orchestrator passes raw audio
+    /// already resampled to the provider's `capabilities().sample_rate`.
+    async fn transcribe(
+        &self,
+        audio: AudioSamples,
+        options: TranscriptionOptions,
+    ) -> Result<ProviderTranscript>;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn provider_trait_is_object_safe() {
+        // Compile-time witness: if the trait stops being object-safe
+        // (generic method, Self-returning method, missing async_trait
+        // attribute) this declaration fails to build. No runtime work.
+        let _: Option<std::sync::Arc<dyn TranscriptionProvider>> = None;
+    }
+
+    #[test]
+    fn provider_id_round_trips_display_and_str() {
+        let id = ProviderId::new("local-whisper");
+        assert_eq!(id.as_str(), "local-whisper");
+        assert_eq!(id.to_string(), "local-whisper");
+    }
+
+    #[test]
+    fn engine_profile_derives_options() {
+        let profile = EngineProfile {
+            engine_id: ProviderId::new("local-whisper"),
+            model_id: None,
+            language: Some("en".to_string()),
+            initial_prompt: Some("Wyrdnote".to_string()),
+        };
+        let opts = profile.to_options();
+        assert_eq!(opts.language, Some("en".to_string()));
+        assert_eq!(opts.initial_prompt, Some("Wyrdnote".to_string()));
+    }
+}