fix(ci): sequence tarball boot after package build

[diegosouzapw]

Summary

• port the release-green pack-artifact/pack-boot race fix from fix(ci): close remaining release-green gaps #9835 to main
• keep package artifact generation parallel with the other slow suites
• run the installed-tarball boot smoke only after the artifact builder succeeds
• record a hard, explicit skip/failure when the artifact builder fails
• add a regression test for the sequencing contract

Why

check:pack-boot consumes dist/server.js, while check:pack-artifact may be the process that creates it in a clean worktree. Running both inside the same Promise.all made the gate nondeterministic. This is the mandatory main companion for the gate/infra fix merged into release/v3.8.50 by #9835.

Validation

• node --import tsx/esm --test tests/unit/validate-release-green.test.ts — 21/21 passed
• focused ESLint — passed
• Prettier — applied to the two touched files
• git diff --check — passed

Related: #9737
Release port: #9835

[diegosouzapw]

Closing as already delivered through the release line: commits 965f85e (pack boot sequencing) and 6d7c221 (changelog fragment), including the matching test behavior, are present in release/v3.8.50. #8875 remains the draft promotion vehicle from that release to main.

[github-actions]

CI Coverage Report

• Coverage job: skipped
• PR test policy: success

Coverage artifact was not available for this run.