RandomSpace + a Space trait + typed ParamRange: the random half of the
C12.1 param-sweep axis (grid shipped in 0028). N seeded uniform draws over
declared continuous ranges, fed to the same enumeration-agnostic sweep core.
Param-only sweep signature and a code-path-disjoint SplitMix64 instance keep
the World-II source-seam firewall (refs #71) intact.
Auto-signed under /boss spec auto-sign: fresh grounding-check PASS and a
unanimous five-lens spec-skeptic panel (criterion, grounding, scope-fork,
ambiguity, plan-readiness all SOUND).
refs #52