feat(providers): add OrcaRouter provider

[JinhaoSong322]

Summary

Adds a named OrcaRouter provider to rig-core, mirroring the existing OpenAI-compatible gateway providers (groq, together, venice). OrcaRouter is an OpenAI-compatible gateway that aggregates thousands of AI models behind one endpoint at https://api.orcarouter.ai/v1. 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.

Changes

• crates/rig-core/src/providers/orcarouter.rs — new provider module implementing OpenAICompatibleProvider:
  • base URL https://api.orcarouter.ai/v1, default model orcarouter/auto
  • completions through the shared GenericCompletionModel / OpenAI Chat Completions path
  • GET /models model listing via the shared lister
  • ORCAROUTER_API_KEY env var for Client::from_env()
• crates/rig-core/src/providers/mod.rs — register the module and list it in the provider doc
• tests/orcarouter.rs + tests/providers/orcarouter/ — live smoke tests (ignored, require ORCAROUTER_API_KEY) for completion, streaming, tools, and model listing
• tests/cassette_cache_prefix.rs / tests/core/provider_layout.rs — register the provider with the layout guards (OpenAI Chat Completions wire family; cache suite not yet recorded)

Verification

• cargo test -p rig-core --lib — 1552 passed, 0 failed
• cargo test -p rig — 203 passed; the only failure is the pre-existing environment-dependent llamacpp::cassette::loaders::loaders_smoke (reproduces on a clean tree; its cassette scrubs REDACTED_PATH which cannot match a local checkout path)
• cargo clippy -p rig-core --all-targets — clean
• cargo fmt --check — clean
• Live smoke tests against the real OrcaRouter API — all 5 pass (completion, streaming, streaming tools, tools roundtrip, model listing) on the pinned 1.94.0 toolchain

Related

Closes #2383

Disclosure: I'm an engineer on the OrcaRouter team.

[gold-silver-copper]

@JinhaoSong322 Hey there, since you are part of the OrcaRouter team, please provide me with an API key/ credits, so that I can properly test and implement OrcaRouter support for Rig. Email me at stephen@playgrounds.network