feat(messaging-ui): KernelClientAdapter — direct-IIOS transport for the SDK

Implements MessagingAdapter over @insignia/iios-kernel-client (browser → IIOS,
token-in): listConversations/openThread/history/send/subscribe/typing/markRead
/react, mapping kernel Message/ThreadSummary/annotations onto the SDK's neutral
types. currentActorId comes from the host's session (senderId space), never
inferred from history — the exact bug the conformance suite kills.

- lives in adapters/ (transport boundary intact — core stays transport-free)
- ships from the ./adapters/kernel-client subpath (kernel-client is an optional
  peer dep; excluded from the main bundle)
- connectKernelAdapter({serviceUrl, token, currentUserId}) convenience
- passes the shared adapter conformance suite (12 tests) over the real
  MessageSocket facade with only the socket.io layer faked
- media/attachments deferred (kernel-client has no presign yet)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/iios-messaging-ui/tsup.config.ts

@@ -6,9 +6,9 @@ export default defineConfig({
   // entry, never reachable from `index`, because it imports vitest, and bundling
   // that into the main barrel would drag a test runner into every consumer's
   // production build.
-  entry: ['src/index.ts', 'src/adapters/mock.ts', 'src/conformance.ts'],
+  entry: ['src/index.ts', 'src/adapters/mock.ts', 'src/adapters/kernel-client.ts', 'src/conformance.ts'],
   format: ['esm'],
   dts: true,
   clean: true,
-  external: ['react', 'react-dom', 'vitest'],
+  external: ['react', 'react-dom', 'vitest', '@insignia/iios-kernel-client'],
 });