docs: spec and implementation plan for CLI telemetry + update check
- docs/superpowers/specs/2026-06-21-cli-telemetry-update-check-design.md
- docs/superpowers/plans/2026-06-21-cli-telemetry-update-check.md
Covers: GET /cli/version, POST /telemetry (Redis HINCRBY), Redis persistence
for existing in-memory metrics (seed + 5min flush + graceful shutdown),
CLI update check goroutine, telemetry goroutine, --help update, MSDL_NO_TELEMETRY opt-out.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>