Add BitRouter to Runtimes, Harnesses & Reference Implementations

[SPIKESPIGEL404]

Summary

• Adds BitRouter, an open-source (Apache-2.0) agent-native Rust LLM router that optimizes your agent with every run — with zero harness changes, every model call becomes reliable, traceable, secure, and cost-effective. It sits inside the harness, fronting multiple providers behind one local endpoint and adding the reliability/control layer harnesses need: cross-protocol routing, an MCP gateway, guardrails, per-request observability, virtual keys, and multi-account failover. Placed alphabetically in Runtimes, Harnesses & Reference Implementations alongside peers like SWE-ReX and Uni-CLI.

Checklist

• The resource is directly relevant to harness engineering
• The link works
• The resource is not already listed
• The description explains the harness angle clearly
• The change is placed in the most appropriate section

Notes

The "zero harness changes / reliable, traceable, secure, cost-effective" framing is the core reliability/control angle this list cares about; description is grounded in concrete capabilities (repo link used, not the homepage).