fix(model): resolve catalog provider API keys from declared env vars

[wangyuxun6699]

Summary

Fixes #339

This PR fixes credential resolution for built-in catalog providers that declare apiKeyEnvVar.

Previously, catalog providers could inherit protocol, default URL, and model defaults, but parseModelConfig ignored apiKeyEnvVar when resolving credentials. As a result, providers such as Anthropic still failed with missing_api_key unless users repeated apiKey: ${ANTHROPIC_API_KEY} in config.

Changes:

• Use catalog apiKeyEnvVar as the default API key source when provider apiKey is absent.
• Keep explicit apiKey config higher priority than catalog defaults.
• Reuse existing resolveApiKey env resolution, trimming, and error behavior.
• Preserve existing behavior for non-catalog providers and ollama.

Tests

Added coverage for:

• Resolving Anthropic catalog credentials from ANTHROPIC_API_KEY.
• Preserving explicit ${ENV_VAR} API key behavior.
• Reporting missing_api_key when the catalog env var is absent.
• Keeping non-catalog providers unchanged when no apiKey is configured.

Verified with:

• npm run build
• node --test --test-timeout 60000 dist/tests/model/parseModelConfig.spec.js
• node --test --test-timeout 60000 dist/tests/model/*.spec.js
• npx tsc -p tsconfig.json --noEmit