fix: retrospective record for CI acceptance-workflow rollback merged without a delivery issue

[LeXwDeX]

Why

PR #400 (fix(ci): restore the proven specgit-accept install strategy) was opened and merged without a specgit delivery issue, violating the SpecGit rule that every merged change rides an issue→PR delivery. The change itself was correct (rolling back the broken pnpm rewrite from parking commit d6ce53a); the process record was missing.

Scope

• Retrospective issue filed (this issue)
• release: memory silent-failure repair + dag-auto routing reduction #399 PR description discloses the causal chain: parking commit d6ce53a (unreviewed workspace changes committed to the 389 branch with a mismatched commit message) → release: memory silent-failure repair + dag-auto routing reduction #399 first main-target PR exposed the broken workflow → fix(ci): restore proven specgit-accept install strategy #400 rolled it back

Acceptance

• The causal chain is visible in release: memory silent-failure repair + dag-auto routing reduction #399's PR description
• This issue closes with the release-train remediation delivery (fix: release-train remediation - harness rollback record, release notes series file, MEMORY live verification #401)

[LeXwDeX]

Retrospective record complete: causal chain disclosed in PR #399 body (Process disclosure section), delivered to main via #403/#399.