Svarog 4.20.2

Audit landings (C-SEL-4 .err sidecar, --split-signal hard-tie,
upfront --output validation, shutdown-hook save on Cmd+Q,
SvarogBootstrap Java-version diagnostic) plus the locale fix and
the post-audit UX fixes (atom tooltip registration, embedded book
collapsibility, C-TAG-2 tooltip soft-fail). See log.md 2026-06-06
for the full release entry.