Fix auxiliary Vertex provider resolution

[hashbender]

Fixes NousResearch#56810.

Summary

• Resolve auxiliary providers from ProviderProfile metadata when hermes_cli.auth.PROVIDER_REGISTRY does not contain non-API-key providers such as Vertex.
• Add Vertex aliases (google-vertex, vertex-ai, gcp-vertex, vertexai) to auxiliary provider normalization.
• Replace the misleading VERTEX_API_KEY explicit-provider error with Vertex OAuth2/ADC guidance for both sync and async auxiliary calls.
• Add regression tests for Vertex alias resolution and Vertex unavailable error text.

Why this is broader than the message-only fixes

NousResearch#56842 and NousResearch#56843 fix the misleading error text. This PR also fixes the resolution path that led to the error in the first place:

• Before this change, resolve_provider_client("google-vertex", ...) normalized to vertex, then looked only in hermes_cli.auth.PROVIDER_REGISTRY.
• vertex is intentionally absent from that registry because it uses OAuth2/ADC, not static API-key env vars.
• That made the existing auth_type == "vertex" branch unreachable for auxiliary tasks, so valid Vertex credentials could still be ignored.
• This PR falls back to ProviderProfile metadata for providers missing from PROVIDER_REGISTRY, which lets Vertex reach the existing Vertex OAuth2 client path while preserving the old API-key path for ordinary providers.

Related context: NousResearch#56688 handles Vertex registry/overlay wiring from another angle. This PR keeps the auxiliary fix local to agent/auxiliary_client.py and does not require making Vertex look like an API-key provider.

Tests

• scripts/run_tests.sh tests/agent/test_auxiliary_client.py tests/hermes_cli/test_vertex_provider.py tests/agent/test_vertex_adapter.py tests/agent/test_bedrock_integration.py tests/agent/test_auxiliary_client_resolve_dedup.py — 371 passed.
• .venv/bin/ruff check agent/auxiliary_client.py tests/agent/test_auxiliary_client.py — passed.
• git diff --check — passed.
• Full scripts/run_tests.sh after installing .[all,dev]: 1818 files, 37336 tests passed, 40 failed, plus tests/run_agent/test_run_agent.py hit the 300s per-file timeout. Observed failures were outside this change area: Anthropic keychain mocked-subprocess tests, macOS systemd/user D-Bus assumptions, macOS /tmp vs /private/tmp path normalization, SSRF-guarded test domains resolving to private/internal addresses, browser/cloud routing environment assumptions, and a long run-agent file timeout. Vertex/auxiliary/provider-profile related tests passed in the full run.

Review

• Self-reviewed the diff for provider registry fallback behavior, Vertex alias canonicalization, non-API-key error guidance, and API-key provider behavior preservation. No blocking issues found.

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Mirror-of: NousResearch#56861
NousResearch#56861