Directory submission fails with server_snapshot.tools.N.visibility: Extra inputs are not permitted

### What happened?

When submitting a remote MCP server to the Connectors Directory (claude.ai/admin-settings/directory/submissions/new), clicking "Submit for review" on the Review step fails every time with a generic banner: "Some fields couldn't be validated by the server. Review the highlighted steps and try again." No step in the sidebar is ever highlighted or marked invalid -- every step (Introduction through Review) shows a green checkmark.

We captured the actual network request via Chrome's net-export (chrome://net-export/) since page-level fetch/XHR interception did not see it (the app appears to hold an early reference to window.fetch). The real request and response are:

POST https://claude.ai/api/organizations/{org_id}/directory/mcp-servers
-> HTTP 400

Response body:
{"type":"error","error":{"type":"invalid_request_error","message":"submission_data.server_snapshot.tools.0.visibility: Extra inputs are not permitted"},"request_id":"req_011CduGxxX7FXD33idfgjExN"}

We reproduced this consistently: with the original connector, after deleting and re-adding the connector from scratch (fresh OAuth grant, default tool permissions), after switching Authentication mode between Dynamic Client Registration and Client ID Metadata Document, and across multiple browsers (Chrome and Safari). Same error every time.

### What did you expect to happen?

The submission should either succeed, or the error banner should point at the actual invalid field/step so we can fix it. Instead the client appears to send a field (visibility) on each tool inside server_snapshot that the submission endpoint's schema does not accept, and this happens unconditionally -- not something we can work around from the connector/server side.

### Steps to reproduce

1. Add a remote MCP server as a custom connector under Settings -> Connectors (we used https://meistron.app/api/mcp).
2. Connect it (OAuth 2.1, either DCR or CIMD -- reproduces with both).
3. Go to claude.ai/admin-settings/directory/submissions/new and fill out all 11 steps of a new directory submission for that connector.
4. On the final Review step, click "Submit for review".
5. Observe the toast: "Some fields couldn't be validated by the server. Review the highlighted steps and try again." -- with no step actually highlighted.
6. Open chrome://net-export/, start logging (with "Include raw bytes" enabled), click submit again, stop logging, and inspect the POST to /api/organizations/{org}/directory/mcp-servers -- it returns HTTP 400 with the visibility error shown above.

### Area

MCP Connector (adding/managing servers)

### MCP Server (if applicable)

Meistron (https://meistron.app/api/mcp)

### Error messages or logs

```shell
Two separate request_ids observed for the same error, captured on different days:

req_011CduGxxX7FXD33idfgjExN
req_011CTKzP6bqTa2xzsN2ZXXP1

Response body (identical shape both times, only request_id differs):
{"type":"error","error":{"type":"invalid_request_error","message":"submission_data.server_snapshot.tools.0.visibility: Extra inputs are not permitted"},"request_id":""}

Captured via chrome://net-export/ against POST https://claude.ai/api/organizations/{org_id}/directory/mcp-servers (HTTP 400). Page-level fetch/XHR patching did not observe this request, which is why we had to fall back to a browser-level capture.
```

### Additional context

_No response_