Use exact benchmark fixture stats

[longlho]

Summary

• replace truncated GitHub API fixture counts with exact archive-derived benchmark stats
• report the actual TS-family file count exercised by the shared benchmark config
• update the README benchmark table to use those exact counts

Validation

• git diff --check
• node --experimental-transform-types benchmarks/run.ts --help
• node --experimental-transform-types benchmarks/run.ts --fixture kibana --skip-build --skip-knip --samples 1 --warmups 0