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/core/src/error.rs

@@ -9,7 +9,7 @@ use crate::types::ModelId;
 /// Implements `Serialize` so errors can be sent to the frontend as
 /// structured JSON rather than opaque strings.
 #[derive(Debug, thiserror::Error, Serialize)]
-pub enum MagnotiaError {
+pub enum Error {
     #[error("model not found: {0}")]
     ModelNotFound(ModelId),
 
@@ -55,7 +55,7 @@ pub enum MagnotiaError {
     },
 }
 
-/// Coarse discriminator for `MagnotiaError::Storage`. The storage crate maps
+/// Coarse discriminator for `Error::Storage`. The storage crate maps
 /// its full typed error onto one of these kinds at the boundary. Backend code
 /// that wants finer-grained branching pattern-matches on
 /// `lumotia_storage::Error` directly.
@@ -70,7 +70,7 @@ pub enum StorageKind {
     Filesystem,
 }
 
-impl From<std::io::Error> for MagnotiaError {
+impl From<std::io::Error> for Error {
     fn from(err: std::io::Error) -> Self {
         Self::Io {
             kind: format!("{:?}", err.kind()),
@@ -80,4 +80,4 @@ impl From<std::io::Error> for MagnotiaError {
     }
 }
 
-pub type Result<T> = std::result::Result<T, MagnotiaError>;
+pub type Result<T> = std::result::Result<T, Error>;

crates/core/src/lib.rs

@@ -9,7 +9,7 @@ pub mod recommendation;
 pub mod tuning;
 pub mod types;
 
-pub use error::{MagnotiaError, Result};
+pub use error::{Error, Result};
 pub use types::{
     AudioSamples, DownloadProgress, EngineName, Megabytes, ModelId, Segment, Transcript,
     TranscriptionOptions,