Fix BIOS Continue EFI build freeze

[redpersongpt]

Summary

• fix BIOS Continue -> Build EFI so accepted BIOS sessions can enter non-destructive EFI build without rerunning the BIOS probe
• align renderer/main/preload/type IPC contracts for guardBuild and buildEFI
• keep destructive paths strict on real biosReady and add regression coverage for build/flash/runtime resolution

Verification

• npm test
• npx tsc -p electron/tsconfig.json --noEmit
• npm run build