Electron Releases

The gn-check CI job regenerates filenames.hunspell.gni and the other derived lists with --check and runs gn check on all three platforms. The electron-chromium-upgrade skill only covered build/siso_revision, so the 158.0.8116.0 roll (#55174) passed its build and failed all three gn-check jobs on a stale hunspell list.

This change:

• has Phase One regenerate every derived list after e sync --3 and says which commit pattern each file needs (chore: update siso revision, chore: update libc++ filenames, or a {CL}: {title} commit for the hunspell list)
• has Phase Two run npm run gn-check and the gen-* --check scripts before declaring success, matching pipeline-segment-electron-gn-check.yml
• fixes the pre-commit hook pre-flight check, which looked in .git/hooks even though husky installs to .husky/_
• documents e build --no-remote -t for when the remote executor fails on toolchain inputs
• adds the chore: update libc++ filenames pattern to the Phase One commit guidelines

🤖 Generated with Claude Code

Notes: none