Part 1 fixes: complete stdout writes, buffered stdin, Rust type names
in schemas, enum variant docs, -32603 for serde errors in handlers,
crate docs and modules. End-to-end check of a generated consumer through
a fake core.
Checkpoint. Known issues, fixed in part 2: short writes on stdout,
byte-wise stdin reads, Result suffix on all result schemas, lost enum
variant docs, serde errors as invalid params, missing item docs.