Move the inline fork-prerequisites result assertion out of the
fork-prereqs-ready job into scripts/github/gate/fork_prereqs.sh (result
passed via the RESULT env var; the job now checks out the repo).
The staged diff also drops the code-quality-gate and test-install-gate
aggregator jobs and wires their members (lint, test, security-codeql,
test-install-make, test-install-pkgmgr) directly into the done job's needs,
which still hard-fails on any upstream failure or cancellation.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>