Add per-adapter architecture docs in event-targets/ directory

- Create docs/architecture/event-targets/ with individual specs:
  in-process, redis, websocket-client, websocket-server,
  worker, iroh-spoke, iroh-hub
- Update event-targets.md to serve as index with topology model
  (symmetric vs fan-out) and adapter status table
- Update architecture.md index to reference new directory

docs/architecture/event-targets/iroh-spoke.md

@@ -0,0 +1,66 @@
+---
+status: draft
+last_updated: 2026-05-07
+---
+
+# Iroh Spoke Event Target
+
+**Import**: `@alkdev/pubsub/event-target-iroh-spoke`
+**Peer dep**: `@rayhanadev/iroh` (optional, NAPI-RS native addon)
+**Status**: Not yet implemented. Needs R&D on binding stability and Deno/NAPI compatibility.
+
+P2P QUIC event target for the spoke (client) side. The spoke initiates the connection and opens the bidirectional stream.
+
+## `createIrohSpokeEventTarget`
+
+```ts
+async function createIrohSpokeEventTarget<TEvent extends TypedEvent>(
+  args: CreateIrohSpokeEventTargetArgs,
+): Promise<TypedEventTarget<TEvent>>;
+```
+
+### `CreateIrohSpokeEventTargetArgs`
+
+| Field | Type | Required | Description |
+|-------|------|----------|-------------|
+| `endpoint` | `Endpoint` | Yes | iroh endpoint (created with `Endpoint.create()`) |
+| `hubNodeId` | `string` \| `NodeId` | Yes | The hub's public key (Ed25519) |
+| `alpn` | `string` | No | Application-layer protocol. Default: `"alkpubsub/1"` |
+
+## Protocol
+
+Single bidirectional QUIC stream per connection. Length-prefixed JSON messages:
+
+```
+[4 bytes: length N][N bytes: JSON payload]
+```
+
+The JSON payload is the `EventEnvelope`:
+
+```json
+{ "type": "call.responded", "id": "uuid-123", "payload": { "output": 42 } }
+```
+
+## Connection Flow
+
+1. Spoke creates `Endpoint`
+2. Spoke calls `endpoint.connect(hubNodeId, alpn)` → `Connection`
+3. Spoke calls `connection.openBi()` → `SendStream` + `RecvStream`
+4. Spoke wraps streams in `IrohSpokeEventTarget`
+5. On disconnect: `RecvStream.readExact()` throws, spoke must reconnect
+
+## Key Properties
+
+- **NAT traversal** — spoke dials hub by `NodeId`, no public IP needed
+- **Cryptographic identity** — `Connection.remoteNodeId()` verifies the hub
+- **Bidirectional** — `dispatchEvent` writes to `SendStream`, `addEventListener` reads from `RecvStream`
+- **Per-connection** — one event target per QUIC connection
+
+## R&D Needed
+
+1. **Binding stability** — `@rayhanadev/iroh` has one author and no tests. API surface is small (10 methods) but needs validation.
+2. **NAPI under Deno** — NAPI-RS `.node` binaries need testing under Deno 2.x.
+3. **Stream multiplexing** — multiple `openBi()` streams on one connection vs. single stream with multiplexed events. Single stream + JSON framing is simpler.
+4. **Reconnection** — `RecvStream.readExact()` throws on connection close. Need to propagate this to listeners and support reconnect.
+
+See [../iroh-transport.md](../iroh-transport.md) for full protocol details, identity, and comparison with WebSocket.