NEXT Athlete OS · v96 RC119 · legacy cleanup / v97 handoff

Base: RC118 pass settings menu modernization.

Scope:
- Active runtime cache-busters no longer carry old version strings.
- Pass settings presentation extracted to a renderer helper.
- Active dashboard class names moved from old rc-prefixed names to next-dashboard-* names.
- Start/rest pass stage compatibility classes removed from active renderer output.
- Historical reference CSS archive removed from deploy payload.
- Added active runtime legacy-reference guard test.

QA notes: docs/RC119_LEGACY_CLEANUP_V97_HANDOFF_QA.md