`replacer` function only called for root context in writer path

[mfiano]

In the around method, the replacer is only called for non-nil contexts, which means within the context of with-object, the context is non-nil and never funcalls the replacer (because context is :object-key). This doesn't match the documentation's recursive JSON.stringify()-like behavior for the manual writer path (with-writer/with-writer* lexical environment).

I tried looking around the tests and noticed the replacer is only tested for stringify.