docs: add supervisor image Helm values to manage-gateways reference

The supervisor init container was introduced in #1154 but the three
`supervisor.image.*` values were missing from the Helm values reference
table in the manage-gateways doc.

Signed-off-by: mesutoezdil <mesudozdil@gmail.com>

Author: mesutoezdil

deploy/helm/openshell/README.md

@@ -47,12 +47,29 @@ The `dev` tags are intended for testing changes ahead of a release. Production d
 
 ## Configuration
 
-See [`values.yaml`](values.yaml) for configurable values. Selected overlays:
+See [`values.yaml`](values.yaml) for the full list of configurable values. Selected overlays:
 
 - [`ci/values-gateway.yaml`](ci/values-gateway.yaml) — gateway-only configuration
 - [`ci/values-cert-manager.yaml`](ci/values-cert-manager.yaml) — cert-manager integration
 - [`ci/values-keycloak.yaml`](ci/values-keycloak.yaml) — Keycloak OIDC integration
 
+Commonly configured values:
+
+| Value | Purpose |
+|---|---|
+| `image.repository` / `image.tag` | Gateway image. Defaults to `ghcr.io/nvidia/openshell/gateway`. |
+| `service.type` | Kubernetes service type. Use `ClusterIP`, `NodePort`, or your platform default. |
+| `server.dbUrl` | Gateway database URL. Defaults to SQLite on the chart-managed persistent volume. |
+| `server.sandboxNamespace` | Namespace where sandbox resources are created. |
+| `server.sandboxImage` | Default sandbox image used when a sandbox does not specify one. |
+| `server.grpcEndpoint` | Endpoint that sandbox supervisors use to call back to the gateway. |
+| `server.sshGatewayHost` / `server.sshGatewayPort` | Public host and port returned to CLI clients for SSH proxy connections. |
+| `server.disableTls` | Run the gateway over plaintext HTTP. Use only behind a trusted transport. |
+| `server.tls.*` | Secret names for server and client mTLS materials. |
+| `supervisor.image.repository` | Repository for the supervisor init container image. Defaults to `ghcr.io/nvidia/openshell/supervisor`. |
+| `supervisor.image.tag` | Tag for the supervisor image. Defaults to the chart's `appVersion` so the supervisor and gateway stay in sync. |
+| `supervisor.image.pullPolicy` | Pull policy for the supervisor image. Defaults to the Kubernetes cluster default when unset. |
+
 ## PKI bootstrap
 
 By default, a pre-install/pre-upgrade hook Job runs `openshell-gateway generate-certs`