agent: lumotia-rebrand — data dir migration shim + paths.rs rename

Phase 5 of the rebrand cascade per locked decision D1 (migrate in place).

crates/core/src/paths.rs:
- Hardcoded subdir strings renamed: magnotia/Magnotia -> lumotia/Lumotia
  across all four OS branches (Linux XDG + dot-legacy, macOS Application
  Support, Windows LOCALAPPDATA, fallback dot-dir).
- Database filename: magnotia.db -> lumotia.db.
- Test path fixtures renamed: /tmp/magnotia-test -> /tmp/lumotia-test.
- New MigrationStatus enum (Migrated / TargetAlreadyExists / NoLegacyFound).
- New migrate_legacy_data_dir() that probes the platform-correct legacy
  magnotia path, renames it to the lumotia equivalent via fs::rename, and
  also renames magnotia.db -> lumotia.db inside if found. Idempotent: safe
  to call on every boot. Refuses to overwrite an existing lumotia dir to
  protect user data.
- Four new unit tests covering all branches via the test-friendly
  migrate_legacy_data_dir_inner that takes an explicit legacy path.

crates/storage/src/database.rs:
- New migrate_legacy_setting_keys(pool) that renames any settings rows
  with key matching magnotia_* to lumotia_*. Single SQL UPDATE with
  NOT EXISTS guard so it leaves rows alone if a lumotia_ row already
  exists. Re-exported from lib.rs.

src-tauri/src/lib.rs:
- Calls migrate_legacy_data_dir(&app_data_dir()) at the start of setup()
  BEFORE database_path() resolves the now-renamed dir. Logs migration
  outcome to lumotia_startup tracing target.
- Calls migrate_legacy_setting_keys(&db) immediately after init_db
  returns. Logs only when rows are actually renamed.

src-tauri/src/{lib,commands/{diagnostics,rituals,transcripts}}.rs +
crates/storage/src/database.rs:
- All in-code references to magnotia_preferences, magnotia_history (in
  comments), and magnotia_morning_triage_last_shown renamed to lumotia_*.

cargo build --workspace passes. cargo test --workspace: 334 pass, 0 fail
(up from 330; +4 paths::tests).

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

src-tauri/src/commands/diagnostics.rs

@@ -335,7 +335,7 @@ async fn generate_diagnostic_report_inner(
 
     if opts.include_settings {
         out.push_str("## Settings (sanitised)\n\n");
-        match lumotia_storage::get_setting(&state.db, "magnotia_preferences").await {
+        match lumotia_storage::get_setting(&state.db, "lumotia_preferences").await {
             Ok(Some(json)) => {
                 out.push_str("```json\n");
                 out.push_str(&sanitise_preferences_json(&json));

src-tauri/src/commands/rituals.rs

@@ -8,13 +8,13 @@
 //!
 //! Stored under the existing SQLite settings table via
 //! `lumotia_storage::{get_setting, set_setting}` — same bag as
-//! `magnotia_preferences`.
+//! `lumotia_preferences`.
 
 use lumotia_storage::{get_setting, set_setting};
 
 use crate::AppState;
 
-const LAST_TRIAGE_KEY: &str = "magnotia_morning_triage_last_shown";
+const LAST_TRIAGE_KEY: &str = "lumotia_morning_triage_last_shown";
 
 /// Returns the YYYY-MM-DD date string stored on the last successful
 /// morning triage dismissal, or `None` if the user has never been

src-tauri/src/commands/transcripts.rs

@@ -28,7 +28,7 @@ use crate::AppState;
 ///
 /// Task 2.5 — `starred`, `manualTags`, `template`, `language`, `segmentsJson`
 /// were added to back the viewer metadata that previously lived only in the
-/// removed `magnotia_history` localStorage cache.
+/// removed `lumotia_history` localStorage cache.
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct TranscriptDto {