agent: lumotia-rebrand — fix Codex cross-model review blockers

Codex independent review found 11 blockers post-cascade. All addressed.

CRITICAL (data-loss / crash):

10. crates/core/src/paths.rs — migrate_legacy_data_dir_inner used
    fs::rename which fails with EXDEV when source + target are on
    different filesystems (encrypted-home, bind mounts, separate
    $XDG_DATA_HOME partition). Combined with the Phase 5 QC fix that
    made migration errors fatal, this would crash on first launch
    for any user whose data dir spans filesystems. Added
    rename_or_copy_tree() that falls back to copy_dir_recursive +
    remove_dir_all on CrossesDevices / errno 18 (EXDEV). Symlinks
    preserved verbatim. Same fallback applied to magnotia.db ->
    lumotia.db inside the dir.

11. Added 4 unit tests: copy_dir_recursive preserves nested
    structure, rename_or_copy_tree same-filesystem happy path,
    is_cross_device classifies CrossesDevices kind + raw errno 18.

Doc residuals (blockers 1-9):

1. crates/cloud-providers/Cargo.toml — "Wyrdnote pending rebrand"
   description.
2. crates/cloud-providers/src/provider.rs — module docs + test
   fixture Wyrdnote refs.
3. crates/transcription/src/orchestrator.rs — module docs + test
   fixture Wyrdnote refs.
4. docs/roadmap/2026-05-10-pkm-phase-tooling-shortlist.md — phase
   name + outputs/wyrdnote path refs.
5. docs/architecture-map/04-llm-formatting-mcp/llm-tests.md —
   MAGNOTIA_LLM_TEST_MODEL env var.
6. .../cloud-providers-stubs.md — MAGNOTIA_API_KEY_*.
7. docs/architecture-map/03-audio-transcription/tests-and-fixtures.md
   — MAGNOTIA_WHISPER_*.
8. docs/gpu-tuning/plan.md — MAGNOTIA_BENCH_RUN.
9. docs/superpowers/specs/2026-05-09-battery-gpu-aware-thread-tuning-
   design.md + corresponding plan — MAGNOTIA_POWER_STATE_OVERRIDE,
   MAGNOTIA_INFERENCE_THREADS.

cargo test --workspace: 343 pass / 0 fail (up from 339; +4 EXDEV
fallback tests).

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

crates/transcription/src/orchestrator.rs

@@ -1,7 +1,7 @@
 //! `Orchestrator` is the single entry point for transcription. Tauri
 //! commands resolve a provider through it; nothing else calls a
 //! provider directly. This is where the AGPL OEM trait boundary meets
-//! Wyrdnote's local engines.
+//! Lumotia's local engines.
 //!
 //! `LocalProviderAdapter` lives here, not as an `impl
 //! TranscriptionProvider for LocalEngine`. The adapter wraps an
@@ -223,7 +223,7 @@ mod tests {
     #[tokio::test]
     async fn orchestrator_dispatches_to_named_provider() {
         let calls = Arc::new(AtomicUsize::new(0));
-        let registry = build_registry_with("canned", "hello wyrdnote", calls.clone());
+        let registry = build_registry_with("canned", "hello lumotia", calls.clone());
         let orchestrator = Orchestrator::new(registry);
 
         let profile = EngineProfile::new(ProviderId::new("canned"));
@@ -232,7 +232,7 @@ mod tests {
             .await
             .expect("dispatch succeeds");
 
-        assert_eq!(result.transcript.text(), "hello wyrdnote");
+        assert_eq!(result.transcript.text(), "hello lumotia");
         assert_eq!(result.inference_ms, 7);
         assert_eq!(calls.load(Ordering::SeqCst), 1);
     }
@@ -264,7 +264,7 @@ mod tests {
 
         let mut profile = EngineProfile::new(ProviderId::new("canned"));
         profile.language = Some("en".to_string());
-        profile.initial_prompt = Some("Wyrdnote".to_string());
+        profile.initial_prompt = Some("Lumotia".to_string());
 
         let _ = orchestrator
             .transcribe(one_second_of_silence(), &profile)