docs: add OrcaRouter to supported providers

[Marc-oss-hub]

Summary

• Adds OrcaRouter to the README provider lists and documents it with a dedicated section in docs/model_providers.md, mirroring the existing OpenRouter and Atlas Cloud sections.

OrcaRouter is an OpenAI-compatible model routing gateway that exposes 150+ models from OpenAI, Anthropic, Google, DeepSeek, Qwen and others behind a single endpoint and API key. It also runs gateway-level, zero-trust security for AI agents on the same endpoint — screening every prompt/response and governing every tool call on a default-deny basis, with no application code changes.

Compatibility

• Existing agent.run("hello") behavior is unchanged, or the change is documented. (docs-only change)
• Existing stream=True behavior is unchanged, or the change is documented. (docs-only change)

Tests

• python -m compileall -q LightAgent (passed)
• PYTHONPATH=. python -m pytest -q tests/test_v065_core.py tests/test_v070_tracing.py tests/test_memory_policy.py (57 passed)
• Live: LightAgent(model="openai/gpt-5.5", api_key=..., base_url="https://api.orcarouter.ai/v1") returned ORCA-OK

Notes

Documentation only. No code, API, or behavior changes.

I'm an engineer on the OrcaRouter team.

[wxai-space]

Thank you for the documentation contribution. The integration direction is compatible with LightAgent because OrcaRouter exposes an OpenAI-compatible endpoint, but a few changes are required before merge:

1. Please use orcarouter/auto as the primary example model, or clearly state that provider model IDs such as openai/gpt-5.5 and anthropic/claude-opus-4.8 are dynamic and must be confirmed in OrcaRouter's current model catalog. This keeps the LightAgent documentation from becoming stale when upstream model availability changes.
2. Please add a link to the official OrcaRouter model catalog or documentation next to that availability note.
3. Please rebase or update this branch against the latest main, which now contains v0.9.7.
4. No GitHub Actions checks are currently reported for this commit. Please push the documentation update so the full repository CI can run. If GitHub requires maintainer approval for the external workflow, we can approve it after the updated commit appears.

Please keep the repository documentation limited to verifiable compatibility/configuration details and avoid long-term guarantees about model availability, routing behavior, or security policy that are controlled by the external service.