Add Electron fuse tests

[wananing]

Summary

• add focused unit coverage for Electron fuse parsing and writing
• cover malformed fuse tables, missing sentinels, absent fuse indexes, no-op writes, and mode preservation

Validation

• node --import tsx --test packages/installer/test/fuses.test.ts
• npm test
• npm run build
• npm run audit (reports existing esbuild low and tar moderate advisories)