js/jco types generation pinned at jco-transpile 0.5.2: fork types stream params as AsyncIterable, host is written against ReadableStream

[lann]

Residual from #345/#347. Every runtime jco path carries the lann/jco fork (jco-transpile-0.6.2-fa6990d), but js/jco's types script stays on exact 0.5.2: the fork's generated host type definitions declare async-import stream parameters as AsyncIterable<number> where webcrypto.js implements against ReadableStream, so just jco::typecheck fails against fork-generated definitions while the runtime is provably unaffected (the full conformance matrix, jco-browser included, ran green on the fork in #347).

Two ways out, pick when the dust settles upstream:

• retype the host's stream handling to the fork's AsyncIterable shape (follow whichever shape upstream jco standardizes — the fork's fixes are heading there, see -I async: future.transfer trampoline const is emitted after the init generator that references it (TDZ ReferenceError at instantiation) lann/jco#34/dx: development-friction debt — shared core crate, generated jco flags, guest wrappers, harness cleanups #35 traffic), then move the pin;
• or, if upstream settles on ReadableStream, the pin moves for free.

Until then the 0.5.2 pin is exact (no ^), so this is a recorded latitude, not drift.