Simplify to transport-only: remove call protocol, add EventEnvelope, expand stream operators

- Remove src/call.ts (PendingRequestMap, CallEventSchema, CallError) — call protocol belongs in @alkdev/operations
- Add EventEnvelope type ({ type, id, payload }) as the cross-platform serialization contract
- Simplify createPubSub: replace PubSubPublishArgsByKey tuple model with PubSubEventMap; publish(type, id, payload) and subscribe(type, id) use explicit id for topic scoping
- Update Redis adapter to serialize/deserialize full EventEnvelope
- Expand operators: add take, reduce, toArray, batch, dedupe, window, flat, groupBy, chain, join
- Remove @alkdev/typebox runtime dependency (was only used by call.ts)
- Remove ./call sub-path export from package.json and tsup config
- Update all architecture docs to reflect transport-only scope, add Worker adapter, remove call protocol references
- Remove docs/architecture/call-protocol.md
- Update AGENTS.md with new source layout and transport-only principle

docs/research/migration.md

@@ -1,5 +1,7 @@
 # Research: `@alkdev/pubsub` Package Extraction
 
+> **Note (2026-05-01):** This document reflects the original migration from alkhub_ts. Since extraction, the architecture has been simplified — `call.ts` (PendingRequestMap, CallEventSchema, CallError) has been removed from this package and moved to `@alkdev/operations`. The `EventEnvelope` type (`{ type, id, payload }`) is now the cross-platform serialization contract. The `PubSubPublishArgsByKey` tuple-based model has been replaced with a simpler `PubSubEventMap`. Stream operators have been expanded beyond `filter`/`map`/`pipe`. See `docs/architecture/` for current spec.
+
 ## Goal
 
 Extract `packages/core/pubsub/` into a standalone `@alkdev/pubsub` package, following the same peer-dependency tree-shaking pattern as `@alkdev/typemap`. Each event target adapter (Redis, WebSocket, Iroh) is an isolated module that only imports its own peer dependency. The core `createPubSub + TypedEventTarget + operators` has no peer deps beyond `@repeaterjs/repeater`.