Custom connector doesn't prompt reauth when OAuth token expires — silently loses tool access

When a custom MCP connector's OAuth access token expires, the server correctly returns `401` with a `WWW-Authenticate` header pointing to `/.well-known/oauth-protected-resource` (per the MCP auth spec). Claude doesn't act on this signal — the tool silently disappears from the conversation with no reauth prompt and no visible error explaining why. The only fix is manually going to Settings → Connectors and disconnecting/reconnecting the connector.

Expected: Claude should either automatically redo the OAuth flow using the discovered protected-resource metadata, or at minimum surface a "this connector needs reauthorization" prompt to the user instead of failing silently.

This matches a known limitation referenced in third-party MCP server docs ("some clients including the Claude app and Claude Code do not yet auto re-initialize on a 404 and require a manual reconnect").