chore: measure javascript-obfuscator cost on electron:build

[krwg]

Summary

Measure wall-clock impact of scripts/obfuscate-after-pack.cjs on electron:build. Confirm it never runs in the electron:dev loop.

Work

1. Time npm run electron:build with obfuscation enabled vs temporarily skipped
2. Document delta (especially if multi-minute on ~33k lines)
3. Verify obfuscation is post-pack only (not electron:dev)

Acceptance

• Numbers recorded in the issue/PR
• Dev loop confirmed free of obfuscation
• Decision noted: keep / make optional / gate behind env flag