local agents: add hermes, claw and opencode. use gemma 4

[burtenshaw]

Note

Low Risk
Documentation-only changes that broaden setup instructions; low risk aside from potential confusion if example commands/model IDs are incorrect.

Overview
Updates the local agents guide to be agent-agnostic (not Pi-specific) and expands setup instructions to include Pi, OpenClaw, Hermes, and OpenCode connecting to a local llama.cpp OpenAI-compatible server.

Refreshes examples/links to use llama.cpp-compatible model browsing and switches the sample model/commands (including llama-agent) to ggml-org/gemma-4-26b-a4b-it-GGUF:Q4_K_M, plus updates the “How it works” diagram to refer to a generic agent.

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[HuggingFaceDocBuilderDev]

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