Implement hrpc with streaming and wire into setup

- 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

com.bridgeswarm.json

@@ -4,9 +4,9 @@
   "path": "ABSOLUTE_PATH_TO_NATIVE_HOST",
   "type": "stdio",
   "allowed_origins": [
-    "chrome-extension://blfnmjfncalojfpcdkddhklpjkjempof/"
+    "chrome-extension://ahihpjhaledlngogjiplpcjigebfigoo/"
   ],
   "allowed_extensions": [
-    "bridgeswarm-7b9cba818d22b161@example.org"
+    "bridgeswarm-395cda49a8e4c8d8@example.org"
   ]
 }