- Add spec/hyperschema and spec/hrpc codegen (scripts/build-hrpc.js)
with unary, request/response-stream, duplex, and send-only commands
- Run build:hrpc and build:protomux from install.sh so setup is one-step
- Native host: add attachHrpc (Protomux channel + generated HRPC),
handlers for ping, streamSum, fetchStream, duplex, notify
- Load HRPC lazily so missing spec does not crash host; use bare-stream
for Duplex under Bare; add bare-stream, compact-encoding deps
