agent: lumotia-rebrand — drop MagnotiaError prefix, now lumotia_core::Error

Phase 3 of the rebrand cascade per locked decision D4. MagnotiaError ->
Error in crates/core/src/error.rs (the crate name already qualifies it).
92 usages across 14 .rs files renamed via word-boundary sed.

One collision required disambiguation: lumotia_storage already had its
own local Error type (introduced by the slop-pass Area A residuals work).
crates/storage/src/error.rs aliases the imported core error as CoreError
on import; the From<Error> for CoreError boundary impl and the
CoreError::Storage construction site use the alias.

cargo build --workspace passes. cargo test --workspace: 330 pass, 0 fail.

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

crates/transcription/src/orchestrator.rs

@@ -22,7 +22,7 @@ use lumotia_cloud_providers::{
     CostClass, EngineProfile, ProviderCapabilities, ProviderId, ProviderKind, ProviderTranscript,
     TranscriptionProvider,
 };
-use lumotia_core::error::{MagnotiaError, Result};
+use lumotia_core::error::{Error, Result};
 use lumotia_core::types::{AudioSamples, TranscriptionOptions};
 
 use crate::local_engine::LocalEngine;
@@ -81,7 +81,7 @@ impl TranscriptionProvider for LocalProviderAdapter {
         if self.engine.is_loaded() {
             Ok(())
         } else {
-            Err(MagnotiaError::EngineNotLoaded)
+            Err(Error::EngineNotLoaded)
         }
     }
 
@@ -93,7 +93,7 @@ impl TranscriptionProvider for LocalProviderAdapter {
         let engine = self.engine.clone();
         let timed = tokio::task::spawn_blocking(move || engine.transcribe_sync(&audio, &options))
             .await
-            .map_err(|e| MagnotiaError::TranscriptionFailed(format!("Task join error: {e}")))??;
+            .map_err(|e| Error::TranscriptionFailed(format!("Task join error: {e}")))??;
         Ok(ProviderTranscript {
             transcript: timed.transcript,
             inference_ms: timed.inference_ms,
@@ -124,7 +124,7 @@ impl Orchestrator {
     pub fn resolve(&self, profile: &EngineProfile) -> Result<Arc<dyn TranscriptionProvider>> {
         self.registry
             .get(&profile.engine_id)
-            .ok_or_else(|| MagnotiaError::ProviderNotRegistered(profile.engine_id.to_string()))
+            .ok_or_else(|| Error::ProviderNotRegistered(profile.engine_id.to_string()))
     }
 
     /// Transcribe audio using the provider named in the profile. The