Adds Squadron declarative framework for building and running multi-agent AI workflows

[ericlakich]

Summary

• Add or update resource(s) related to harness engineering

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\

This pull request adds a new entry to the list of AI agent harnesses in the README.md file, highlighting the Squadron framework.

New AI agent harness documentation:

• Added a reference to Squadron, a declarative framework for building and running multi-agent AI workflows, to the harness comparison list in README.md.

Notes

Squadron is a declarative framework for building and running multi-agent AI workflows. You describe agents, tools, models, and the task graph entirely in HCL configuration — Squadron’s runtime handles orchestration, state, dependency resolution, conditional routing, persistence, and resume. No Python glue code, no LangChain-style call chains, no hand-rolled state machines.