fix(storage): protect Yomitan profiles across Electron runtime changes

- Block unsupported or downgraded Electron runtimes before loading profile storage
- Isolate development profiles and guard against unexpected dictionary loss

changes/electron43-profile-storage-safety.md

@@ -0,0 +1,6 @@
+type: fixed
+area: dictionary
+
+- Upgraded the desktop runtime to Electron 43.4.1 and added profile guards that block unsupported runtimes and Electron downgrades before Yomitan storage is loaded.
+- Development launches now use a separate `SubMiner-dev` profile unless production-profile access is explicitly requested.
+- Automatic character-dictionary changes now stop when a previously non-empty Yomitan profile suddenly reports zero dictionaries.