Make AgentRouter public-safe

[fschrhunt]

Summary

• replace the public third lane with generic local instead of the private Huma name
• add configurable laneBranches so private deployments can map local to any local workspace branch
• remove personal account/org/path examples from public docs and tests
• keep OpenClaw execution behind AGENT_ROUTER_LOCAL_AGENT

Verification

• pnpm verify

Notes

• Fischer merges manually.