add_connection advertised an empty `{ properties: {} }` while the server
validated strictly, so clients could not see field types or the required
`type` literal and sent port/verifyTls as strings.
Cause: the connection schema was wrapped in `.superRefine`, producing a
ZodEffects with no `.shape`. The MCP SDK's normalizeObjectSchema returns
undefined for it and falls back to EMPTY_OBJECT_JSON_SCHEMA. update_connection
passed a raw shape, so it serialized fine - hence the asymmetry.
Split the schema: a strict z.object (connectionObjectSchema) is advertised as
the wire schema, and the refined connectionConfigSchema is passed as a new
optional parseSchema applied in the handler. Strict unknown-key rejection and
the apiKey-or-user+password check are both preserved. fullSchema is now typed
as a ZodObject so a ZodEffects can no longer be passed by mistake.
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