lib/active-sprint:
- New helpers: getActiveSprintIdFromSettings, setActiveSprintInSettings,
clearActiveSprintInSettings — all read/write user.settings.layout.activeSprints.
- resolveActiveSprint(productId, userId) — userId now required, falls back
to first OPEN, then most recent CLOSED sprint.
- Cookie helpers (getActiveSprintIdFromCookie/setActiveSprintCookie/
clearActiveSprintCookie) removed.
Callers updated to pass session.userId. The cookie-based fallback path
is gone — `actions/active-sprint.ts` and `actions/sprints.ts` will be
updated in the next commit (T-917).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>