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)

tsup.config.ts

@@ -0,0 +1,14 @@
+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',
+});