Add call protocol module with streaming support

New sub-path export @alkdev/pubsub/call providing:
- CallEventSchema (TypeBox schemas) for call.requested/responded/part/completed/aborted/error
- PendingRequestMap with call() (request/response) and subscribe() (streaming via Repeater)
- CallError class and CallErrorCode constants
- Scoped topic subscriptions (call.responded:{requestId}) to avoid O(n) fanout
- subscribe() yields call.part events until call.completed or call.error,
  with automatic call.aborted on consumer break

Also adds @alkdev/typebox as runtime dependency and architecture doc.

package.json

@@ -26,6 +26,16 @@
         "types": "./dist/event-target-redis.d.cts",
         "default": "./dist/event-target-redis.cjs"
       }
+    },
+    "./call": {
+      "import": {
+        "types": "./dist/call.d.ts",
+        "default": "./dist/call.js"
+      },
+      "require": {
+        "types": "./dist/call.d.cts",
+        "default": "./dist/call.cjs"
+      }
     }
   },
   "publishConfig": {
@@ -52,7 +62,9 @@
     "quic"
   ],
   "license": "MIT OR Apache-2.0",
-  "dependencies": {},
+  "dependencies": {
+    "@alkdev/typebox": "^0.34.49"
+  },
   "peerDependencies": {
     "ioredis": "^5.0.0"
   },