readConfigKey / gstack_read_config_key return the most restrictive
telemetry, memorable_recall, codex_reviews and update_check across the
resolved root and ~/.gstack; other keys read the resolved root only.
gstack-config set reports an overriding root with the exact override
command, list shows the winning root and a root-variable disagreement line.
gstack-gbrain-repo-policy get merges deny/read-only tiers. gstack-egress
reads through readConfigKey. test-setup.ts strips inherited
GSTACK_STATE_ROOT/GSTACK_STATE_DIR and redirects the legacy root.