feat(sdk): P2.5 @insignia/iios-kernel-client — REST + socket facade

MessageSocket (open/send/read/typing via emitWithAck, reconnect re-opens thread,
no socket.io types leak) + RestClient (ingest/getThreadMessages/sendMessage).
tsup ESM+dts. Facade unit test with injectable fake socket (3 tests).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-kernel-client/package.json

@@ -0,0 +1,23 @@
+{
+  "name": "@insignia/iios-kernel-client",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "main": "dist/index.js",
+  "module": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "exports": { ".": { "types": "./dist/index.d.ts", "import": "./dist/index.js" } },
+  "files": ["dist"],
+  "scripts": {
+    "build": "tsup",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@insignia/iios-contracts": "workspace:*",
+    "socket.io-client": "^4.8.1"
+  },
+  "devDependencies": {
+    "tsup": "^8.3.5",
+    "typescript": "^5.7.3"
+  }
+}