Use final AsDecided repository paths

[tcballard]

Summary

• present the suite as AsDecided Benchmarks and update canonical repository links
• replace every retired Python-engine CI install with the checksum-verified native asdecided-core 0.23.1 release
• point executable seams at decided while preserving stable RAC benchmark arm vocabulary
• remove unsupported generated frontmatter exposed by native validation

Verification

• root benchmark battery: 54 passed against native decided
• autonomous-QA battery: 40 passed, 2 skipped locally; five localhost-bound tests could not run in the managed sandbox
• installer bash -n
• schema JSON parses
• git diff --check