[Gap]: Document the complete Connector Gateway deployment contract

What needs documentation?

The Configure the Connector Gateway page currently shows only:

• global.stacklok.connectorGateway.enabled
• global.stacklok.connectorGatewayId
• global.stacklok.authServerIssuer

That is not enough to deploy a working Connector Gateway. The chart requires a coupled set of auth-server, incoming-auth, directory, key-management, storage, corporate-IdP, and Enterprise Manager values. Operators currently discover them one failure at a time from Helm errors, pod logs, and the chart's very long values.yaml comments.

Add a complete, task-oriented configuration path that covers at least:

• vmcpConfig.incomingAuth.type: oidc, issuer, audience/resource, and how those values must match the auth server's allowed_audiences.
• enterpriseConfig.authServer, including its schema, upstream behavior, storage contract, and the fact that auth-less mode is not supported.
• kek and authServerKeys, including the production recommendation to use existing Secrets rather than render-unstable generated values.
• enterpriseConfig.directory.addr and binding claims.
• The two supported Directory transport arms:
  • production TLS, projected ServiceAccount token, caller issuer/audience, and subject allowlists on Enterprise Manager;
  • the development-only cleartext configuration, which currently requires matching client and server flags.
• The corporate primary IdP's audience/client requirements for both cloud-ui and the Connector Gateway control plane.
• The Enterprise Manager platform-admin role/binding required to use the admin connector/directory endpoints. The current directory landing page says "The platform admin grant covers" this work but does not show how to create that grant or identify admin.enterprise.stacklok.com.
• A verification sequence that tests login, gateway registration, an authenticated control-plane call, and the data-plane MCP endpoint separately.

Prefer one complete secure example, followed by focused alternatives, rather than making readers assemble fragments from component chart comments.

Context and references

This gap surfaced while moving stacklok-enterprise-demo-sandbox to Stacklok Enterprise Platform v0.17.0.

Related platform issues found during the same deployment:

• https://github.com/stacklok/stacklok-enterprise-platform/issues/4307
• https://github.com/stacklok/stacklok-enterprise-platform/issues/4309
• https://github.com/stacklok/stacklok-enterprise-platform/issues/4312

Relevant source pages:

• docs/platform/enterprise-platform/configure-connector-gateway.mdx
• docs/platform/enterprise-platform/deployment.mdx
• docs/platform/enterprise-platform/configure-identity.mdx
• docs/platform/enterprise-directory/index.mdx

Use case

As a platform operator, I need to enable Connector Gateway from a single supported checklist and understand which values form one contract across the umbrella chart, so that a successful Helm install produces a usable login, control plane, and MCP data plane without iterative crash-loop debugging.

Start with docs/platform/enterprise-platform/configure-connector-gateway.mdx and compare it with deployment.mdx, configure-identity.mdx, and docs/platform/enterprise-directory/index.mdx, then trace the referenced chart values and comments. Document one complete secure configuration, focused alternatives, and separate checks for login, gateway registration, an authenticated control-plane call, and the MCP data plane. Done means operators can follow one supported checklist without assembling undocumented contract details.