Add client credentials support to everything-client

[pcarleton]

Summary

This PR adds support for OAuth 2.0 client credentials flow testing in the conformance suite, enabling both private_key_jwt and client_secret_basic authentication methods.

Changes

New Files

• src/schemas/context.ts - Zod schema for conformance test context with discriminated union for auth scenarios

Modified Files

• examples/clients/typescript/everything-client.ts

  • Added runClientCredentialsJwt and runClientCredentialsBasic handlers
  • Uses PrivateKeyJwtProvider and ClientCredentialsProvider from the SDK
  • Made handlers exportable for inline testing

• src/runner/client.ts

  • Include scenario name in context for discriminated union parsing

• src/scenarios/client/auth/test_helpers/testClient.ts

  • Set environment variables for inline client runners

• src/scenarios/client/auth/index.test.ts

  • Added scenario client map to route client credentials scenarios to specific handlers
  • Removed client credentials from skip list

• src/scenarios/client/auth/client-credentials.ts

  • Accept both trailing slash forms for JWT audience (per RFC 3986, URLs with and without trailing slash are equivalent)

Testing

All 56 tests pass, including the two new client credentials tests:

• auth/client-credentials-jwt
• auth/client-credentials-basic

Also verified with the Python SDK conformance client:

node dist/index.js client --command "uv run --directory ~/code/mcp/python-sdk/examples/clients/conformance-auth-client python -m mcp_conformance_auth_client auth/client-credentials-jwt" --scenario auth/client-credentials-jwt
# ✅ OVERALL: PASSED (8/8 checks)

node dist/index.js client --command "uv run --directory ~/code/mcp/python-sdk/examples/clients/conformance-auth-client python -m mcp_conformance_auth_client auth/client-credentials-basic" --scenario auth/client-credentials-basic
# ✅ OVERALL: PASSED (8/8 checks)

[pkg-pr-new]

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commit: 788db58