agent: lumotia-rebrand — tauri productName, identifier, window title

Phase 6 of the rebrand cascade per locked decision D2.

src-tauri/tauri.conf.json:
- productName: "Magnotia" -> "Lumotia"
- identifier:  "uk.co.corbel.magnotia" -> "consulting.corbel.lumotia"
- window title: "Magnotia" -> "Lumotia"

D2 picks the reverse-DNS of corbel.consulting (the actual domain CORBEL
trades under) over the prior uk.co.corbel.* convention. This is the
identity the OS uses for installed-app keying, so the first launch under
the new identifier will look fresh to Tauri's plugin state (window-state,
autostart). Per D1 the user-data dir is migrated by lumotia_core::paths
on first boot, so transcripts and settings survive.

cargo build --workspace passes. cargo test --workspace: 339 pass, 0 fail.

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

src-tauri/tauri.conf.json

@@ -1,8 +1,8 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
-  "productName": "Magnotia",
+  "productName": "Lumotia",
   "version": "0.1.0",
-  "identifier": "uk.co.corbel.magnotia",
+  "identifier": "consulting.corbel.lumotia",
   "build": {
     "beforeDevCommand": "npm run dev:frontend",
     "devUrl": "http://localhost:1420",
@@ -12,7 +12,7 @@
   "app": {
     "windows": [
       {
-        "title": "Magnotia",
+        "title": "Lumotia",
         "width": 1020,
         "height": 720,
         "minWidth": 960,