feat(sdk): P5.1 @insignia/iios-adapter-sdk — ChannelAdapter contract + HMAC webhook adapter + sandbox + fixtures

Contract (capability incl. requiresFollowupFetch seam, verifySignature, normalize,
fetch?, send), HMAC-SHA256 sign/verify (timing-safe), reference WebhookAdapter
(normalize→IngestInteractionRequest), SandboxSink (no network), email/whatsapp
fixtures. CJS build (consumed by the NestJS service). 4 tests; boundary updated.

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

packages/iios-adapter-sdk/tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "types": ["node"]
+  },
+  "include": ["src/**/*.ts"],
+  "exclude": ["src/**/*.test.ts"]
+}