Add AgentPlane to harness implementations

[densmirnov]

Hi - I would like to add AgentPlane to this list.

Disclosure: I maintain AgentPlane.

Why it fits:
AgentPlane is not a generic agent tool or model framework. It is a local, Git-native workflow control harness that makes task records, workflow policy, verification evidence, and closure state explicit repository artifacts for repo-local coding-agent work.

Suggested category:
Runtimes, Harnesses & Reference Implementations. This seems closest because the project is an inspectable implementation of a workflow-control harness rather than an article, benchmark, or generic agent framework.

Entry added:
AgentPlane - Git-native workflow control harness for repo-local coding-agent work. It makes task records, workflow policy, verification evidence, and closure state explicit repo artifacts, which is useful for auditable and resumable agent work.

Verification:

• git diff --check

Happy to adjust category, wording, or remove if this is outside scope.

[densmirnov]

Quick update: I rebased this branch onto the current main and resolved the README conflict with the newer harness entries.

git diff --check passes locally. Happy to adjust the wording or placement if needed.