Record Phase 47 main-path containment

[YSCJRH]

Summary

• Adds a Phase 47 main-path containment report for issue Phase 47: main-path product containment #369.
• Records direct evidence that the default path remains compare/evidence/eval centered while legacy packet-heavy tooling stays secondary.
• Documents that no frontend, artifact, schema, scenario DSL, run trace, or MCP contract change was needed.

Fixes #369

Validation

• 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 docs/plans/phase-47-main-path-containment-2026-05-16.md
• git diff --check

Notes

• No frontend code changed, so npm run build --prefix frontend was not required for this docs-only containment report.