Sync Phase 47 queue state

[YSCJRH]

Summary

• Update README, current-state baseline, phase execution queue, automation roadmap, and Phase 47 gate docs to reflect the approved Phase 47 queue.
• Record milestone Phase 47 - Boundary Readiness and Successor Hygiene, exit gate Phase 47 exit gate #365, and ready work items Phase 47: sync repo truth to successor queue #366-Phase 47: main-path product containment #369.
• Preserve the boundary that untracked private-beta/kernel/design-system plans remain candidate inputs only.

Test Plan

• python scripts/check_no_secrets.py
• python -m backend.app.cli audit-github-queue --repo YSCJRH/mirror-sim
• python -m backend.app.cli classify-lane --files README.md docs/plans/automation-roadmap.md docs/plans/current-state-baseline.md docs/plans/phase-47-successor-gate-2026-05-16.md docs/plans/phase-execution-queue.md
• git diff --check
• npm run build --prefix frontend - not run; docs-only change with no frontend code touched

Fixes #366