Set up project structure, source files, and architecture docs

- Copy core source from alkhub_ts/packages/core/pubsub/ with import path fixups
  (typed_event_target.ts → types.ts, .ts → .js extensions)
- Make PubSubPublishArgsByKey exported (was private type, needed by barrel)
- Add package.json with sub-path exports and optional peer deps (ioredis)
- Add tsup.config.ts with multi-entry + splitting for tree-shaking
- Add tsconfig.json, vitest.config.ts, .gitignore
- Add AGENTS.md with project conventions and adapter checklist
- Add architecture docs following taskgraph/alkhub pattern:
  docs/architecture/README.md, api-surface.md, event-targets.md,
  iroh-transport.md, build-distribution.md
- Add ADRs: 001-graphql-yoga-fork, 002-tree-shake-pattern
- Copy migration research doc to docs/research/migration.md
- Dual-license MIT OR Apache-2.0 (matching taskgraph)

docs/architecture/build-distribution.md

@@ -0,0 +1,113 @@
+---
+status: draft
+last_updated: 2026-04-30
+---
+
+# Build & Distribution
+
+Dependencies, project structure, tree-shaking, sub-path exports, and build targets.
+
+## Dependencies
+
+| Package | Type | Purpose |
+|---------|------|---------|
+| `@repeaterjs/repeater` | direct | Small (~3KB). Core async iterable primitive for `subscribe()`. |
+| `ioredis` | peer (optional) | Redis client. Only imported by `event-target-redis.ts`. Type-only import at compile time. |
+| `@rayhanadev/iroh` | peer (optional, future) | Iroh NAPI-RS binding. Only imported by `event-target-iroh.ts`. |
+
+No other external dependencies. No logger dependency.
+
+## Project Structure
+
+```
+@alkdev/pubsub/
+  src/
+    index.ts              # Barrel: re-exports core API
+    types.ts              # TypedEvent, TypedEventTarget, etc.
+    create_pubsub.ts      # createPubSub factory
+    operators.ts          # filter, map, pipe
+    event-target-redis.ts # createRedisEventTarget (peer dep: ioredis)
+    # Future adapters (each is its own entry point + peer dep island):
+    # event-target-websocket.ts  # peer dep: none (web standard)
+    # event-target-iroh.ts       # peer dep: @rayhanadev/iroh
+  test/
+    create_pubsub.test.ts
+    operators.test.ts
+    event-target-redis.test.ts
+    # event-target-websocket.test.ts
+    # event-target-iroh.test.ts
+  docs/
+    architecture.md
+    architecture/
+    research/
+  package.json
+  tsconfig.json
+  tsup.config.ts
+  vitest.config.ts
+```
+
+## Sub-Path Exports
+
+We use explicit sub-path exports rather than barrel-only + tree-shaking. Each adapter is importable by its own path:
+
+```json
+{
+  "exports": {
+    ".": { ... },
+    "./event-target-redis": { ... },
+    "./event-target-websocket": { ... },
+    "./event-target-iroh": { ... }
+  }
+}
+```
+
+### Why Sub-Path Exports
+
+- **Explicit** — doesn't rely on bundler tree-shaking behavior
+- **Peer dep isolation** — `import from '@alkdev/pubsub/event-target-redis'` makes the dependency on ioredis explicit at the import site
+- **Consistent with typemap pattern** — typemap's peer deps (zod, valibot, typebox) are each their own module; sub-path exports make this explicit at the package boundary
+
+Sub-path entries are added as adapters are implemented. The barrel `index.ts` also re-exports everything for convenience — consumers who want tree-shaking can import from the barrel and rely on their bundler.
+
+## Peer Dependencies
+
+| Peer Dep | Required By | Optional |
+|----------|-------------|----------|
+| `ioredis@^5.0.0` | `event-target-redis` | Yes |
+| `@rayhanadev/iroh` | `event-target-iroh` (future) | Yes |
+
+Optional peer deps means `npm install @alkdev/pubsub` does NOT install ioredis or iroh. Consumers opt in by installing the peer dep and importing from the sub-path.
+
+## Build
+
+- **Tool**: `tsup` — produces dual ESM + CJS with declarations automatically
+- **Entry points**: `src/index.ts`, `src/event-target-redis.ts`, plus future adapters
+- **Format**: ESM + CJS
+- **Target**: `es2022`
+- **Splitting**: enabled (tsup code splitting for shared chunks)
+
+```ts
+// tsup.config.ts
+import { defineConfig } from 'tsup';
+
+export default defineConfig({
+  entry: ['src/index.ts', 'src/event-target-redis.ts'],
+  format: ['esm', 'cjs'],
+  dts: true,
+  sourcemap: true,
+  clean: true,
+  splitting: true,
+  target: 'es2022',
+});
+```
+
+## Testing
+
+- **Runner**: `vitest` — matches taskgraph, natural fit with tsup/Node build pipeline
+- **Config**: `vitest.config.ts` with `globals: true`
+
+## Targets
+
+- **Publish**: npm (`@alkdev/pubsub`)
+- **Runtime**: Node 18+, Deno, Bun — pure JS (except iroh adapter which requires NAPI-RS)
+- **Deno compatibility**: Source is standard TypeScript with no Deno-specific APIs. Deno can import from npm or JSR.