feat(llm): add OrcaRouter provider 🤖🤖🤖🤖

[XiaoHuo888-hue]

Description

This adds a dedicated OrcaRouter provider to the giskard-llm routing layer, mirroring how the existing named providers (azure/, azure_ai/) are wired. A model string like orcarouter/anthropic/claude-haiku-4.5 now routes through the new orcarouter registry entry to https://api.orcarouter.ai/v1 using an ORCAROUTER_API_KEY.

Why a named provider rather than the generic OpenAI-compatible endpoint? Named providers are the established pattern in this library (azure/, azure_ai/, google/, anthropic/), and named routers such as orcarouter/auto pick an upstream per request, so the registry entry keeps model routing and error attribution consistent with the other named providers. OrcaRouter is an OpenAI-compatible gateway that exposes 150+ models from OpenAI, Anthropic, Google, DeepSeek, Qwen, MiniMax and xAI behind one API key, and it also provides gateway-level security controls for AI agents.

Changes:

• New libs/giskard-llm/src/giskard/llm/providers/orcarouter.py — OrcaRouterProvider, an OpenAIProvider subclass that defaults base_url to https://api.orcarouter.ai/v1 and reads ORCAROUTER_API_KEY (mirrors the AzureOpenAIProvider pattern).
• libs/giskard-llm/src/giskard/llm/routing.py — register orcarouter in _PROVIDER_REGISTRY.
• libs/giskard-llm/README.md — add the orcarouter/ row to the provider reference table.
• Tests in test_providers.py (transport config, env-key + endpoint defaults) and test_routing.py (model-string parsing, unconfigured registry lookup).

Verification:

• uv run --directory libs/giskard-llm pytest tests -m "not functional" — 222 passed, 7 skipped.
• ruff check / ruff format --check — clean; basedpyright --level error — 0 errors.
• Live: acompletion("orcarouter/openai/gpt-5.5", ...) and aembedding("orcarouter/openai/text-embedding-3-small", ...) against https://api.orcarouter.ai/v1 both returned HTTP 200.

Related Issue

N/A

Type of Change

• 📚 Examples / docs / tutorials / dependencies update
• 🔧 Bug fix (non-breaking change which fixes an issue)
• 🥂 Improvement (non-breaking change which improves an existing feature)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🔐 Security fix

Coding agents

This PR was opened by an autonomous agent; per the repo's PR rules the title ends with the required 🤖🤖🤖🤖 marker, and the author read AUTONOMOUS.md before opening it.

Checklist

• I've read the CODE_OF_CONDUCT.md document.
• I've read the CONTRIBUTING.md guide.
• I've written tests for all new methods and classes that I created.
• I've written the docstring in NumPy format for all the methods and classes that I created or modified.
• I've updated the uv.lock running uv lock (only applicable when pyproject.toml has been modified)

I'm an engineer on the OrcaRouter team.