Make bench CLI load TypeScript benchmarks

[HeyGarrison]

Summary

The bench CLI couldn't execute the new benchmarks/reliability/sandbox-opencode.bench.ts file because plain Node doesn't resolve .ts source or its .js→.ts imports.

• packages/benchsdk-runner/src/bin.ts: registers the tsx ESM loader at startup.
• packages/benchsdk-runner/package.json: adds tsx as a runtime dependency and points the bench binary at the ESM build (./dist/bin.js) so the bin and any loaded TypeScript benchmark resolve the same @benchsdk/runner instance.
• package.json and .github/workflows/reliability-tensorlake-opencode.yml: switch the reliability benchmark back to bench run ....

This removes the tsx packages/benchsdk-runner/dist/bin.js indirection. pnpm typecheck, pnpm --filter @benchsdk/runner test, and a dry bench run of the reliability benchmark all pass (the run fails as expected with a dummy TENSORLAKE_API_KEY, but it loads the module and reaches the Tensorlake provider step).

Link to Devin session: https://app.devin.ai/sessions/754c6cb646a146a0b6c883eae4b613b1
Requested by: @HeyGarrison

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.