DevEx: make north-star2-verify presenter gate (#1865)

[PurHur]

Summary

• Add script/north-star2-verify.sh and make north-star2-verify — North Star 2 presenter bundle mirroring #1845 UX (--require-llvm, --skip-llvm-tail).
• Steps: phpc doctor --gates → inventory --check → bootstrap-wave-check → M2 spine link + VM smoke (LLVM) → M3 HelloWorld probe + M4 loop --dry-run tail.
• Wire docs (bootstrap-selfhost.md, local-ci-matrix.md, README) and NorthStar2VerifyScriptTest.

Test plan

• vendor/bin/phpunit --filter NorthStar2VerifyScriptTest (Docker php-compiler:22.04-dev)
• vendor/bin/phpunit --filter testCiFastHonorsNorthStar2VerifyGate
• Full make north-star2-verify with LLVM 9 (long-running; M2 spine link + tail)

docker run --rm -i -w /compiler php-compiler:22.04-dev bash -lc '
  tar -xf - < repo.tar && composer install --ignore-platform-reqs -q
  script/apply-patches.sh && script/install-llvm9.sh
  make north-star2-verify
'

Closes #1865

Made with Cursor

[PurHur]

Superseded by #2046 (merged on master); closing duplicate.