Preserve test meaning across CI platforms

Owner authorization requires successful exact-head CI before merging the public consolidation. Allowed paths are the synthetic runs/knowledge/pack test fixtures, temporary PostgreSQL test helper, unit runner, CI workflow and their tests. No production sandbox default or professional rule is relaxed.

Functional fixtures follow the existing synthetic knowledge-world policy: require OS isolation where available, and explicitly report its absence when exercising trusted synthetic functions without it. Production callers still require isolation by default, and the direct default-refusal tests remain. The change adds no skip.

A terminating signal now waits for each temporary postmaster’s bounded shutdown before removing its data directory. The original exit-hook fallback remains. This removes the Linux filesystem cleanup race; the existing SIGTERM test retains its signal, directory-removal and closed-port assertions.

Parser wall-time bounds run in their own single-worker CI partition, without another test worker competing on the same runner. Their 2-second and 5-second assertions remain unchanged. A file-set test proves the two unit partitions are disjoint and cover every original tracked unit test; each partition keeps its count/skip summary, and the stable Unit tests status fails unless every partition succeeds. No test is excluded through a skip pattern or continue-on-error.