Hoist the v6.0.0 release commit to the tip of main after refreshing
pnpm-lock.yaml to track the cascade-added readme-fleet-shape-guard
hook (CI was failing on ERR_PNPM_OUTDATED_LOCKFILE under
--frozen-lockfile).

package.json `version` is unchanged (already at 6.0.0); this commit
exists to satisfy the fleet rule that the bump commit be the LAST
commit on the release — the v6.0.0 tag will be force-moved to here
so it sits on a green CI commit with a current lockfile.