feat: add Grok Build CLI provider

[canderson26]

Summary

Adds a first-class grok-build provider backed by the local Grok Build CLI.

• Registers grok-build in the provider registry, model catalog, aliases, model picker, runtime resolver, and auxiliary client path
• Adds GrokCliClient, an OpenAI-compatible shim around grok --prompt-file for headless turns
• Defaults to --no-memory --disable-web-search --max-turns 1 --output-format plain --effort xhigh
• Supports HERMES_GROK_BUILD_COMMAND, GROK_CLI_PATH, HERMES_GROK_BUILD_ARGS, and HERMES_GROK_BUILD_EFFORT
• Sets Grok Build context metadata to 512k for the CLI transport and documents setup

Testing

• venv/bin/python -m py_compile agent/grok_cli_client.py agent/model_metadata.py hermes_cli/auth.py hermes_cli/models.py hermes_cli/runtime_provider.py hermes_cli/providers.py hermes_cli/model_normalize.py hermes_cli/model_switch.py hermes_cli/main.py hermes_cli/setup.py agent/auxiliary_client.py run_agent.py tests/agent/test_grok_cli_client.py tests/agent/test_model_metadata_local_ctx.py tests/hermes_cli/test_api_key_providers.py tests/hermes_cli/test_model_validation.py tests/run_agent/test_run_agent.py
• venv/bin/python -m pytest tests/agent/test_grok_cli_client.py tests/agent/test_model_metadata_local_ctx.py tests/hermes_cli/test_api_key_providers.py tests/hermes_cli/test_model_validation.py tests/run_agent/test_run_agent.py::test_aiagent_uses_grok_cli_client -q

Notes

This provider relies on an already-authenticated local Grok Build CLI session. Run grok login and confirm grok models includes grok-build.

[alt-glitch]

Resubmission of #26698 (closed). See also competing xAI provider PRs: #25968, #26437.

[canderson26]

Happy to coordinate with #25968.

I think the scopes are complementary rather than competing:

• feat(providers): add first-class xAI (Grok) OAuth provider with Grok CLI auto-import #25968: xAI OAuth / Grok API-style provider
• This PR: local Grok Build CLI backend for the grok-build product/model

If preferred, I can rebase after #25968 lands and reuse any shared xAI provider registry/auth helpers, but I’d keep xai-oauth and grok-build as distinct providers because the transport and available model surface are different.

[canderson26]

Closing this for now. The fork live branch is back at upstream parity, and we will let the broader xAI provider work settle in the community rather than carrying a separate Grok Build CLI provider PR.