Refresh Walmart Minimum Stress Path date

[tomtoto757]

Summary

• refresh the verified Walmart Minimum Stress Path sighting to Aug 27, 2026
• re-sort the question bank and refresh date badges with the repository freshness script
• keep the change scoped to README.md

Verification

• python3 scripts/refresh-freshness.py (second pass: 0 marker changes, 0 reordered rows)
• python3 -m unittest scripts/test_sync_practice_formats.py (10 tests passed)
• git diff --check
• verified 1,986 rows remain newest-first, all routes unique, and the Walmart row has exactly six pipes and two matching FastPrep URLs
• verified the public practice route returns HTTP 200

Independent review

Reviewed commit 4d62452e734d0111d201263cb5067d959e4f35eb against 3c98ad57c68670b3cfb001a50c7818d470548683 by a separate review agent. No P0-P3 findings; only README.md changed and the deterministic freshness output matched exactly.