Update custom connector

Updates a custom connector. config is REPLACED wholesale when present — send the complete definition, since anything omitted is gone. label and category are ordinary merge-patch fields. Org-owned connectors only, and the caller needs edit access (ownership or an edit share). Existing connections keep working, but tools removed from the config stop resolving in every toolbox that names them. A remote MCP connector (kind: "remote_mcp") takes a different body: label, category, logo, description, auth_config (custom sign-in only; replaces the declaration whole, and the response carries reconnect_required: true when its fields changed so existing connections must sign in again), client_id / client_secret (oauth_client only; an omitted secret keeps the stored one) and omit_refresh_scope (OAuth only, else 400 omit_refresh_scope_not_oauth; true sets it, false removes it, read at the next token refresh, so no reconnect_required) and connect_notes / connect_notes_link (OAuth only, else 400 connect_notes_not_oauth; null clears; stored in place in the OAuth config as permissions_text / documentation_link, so no reconnect_required). Its url cannot be changed (400: it would send members' tokens to a different host — create a new connector) and neither can its raw config (400).