Remove CLAUDE.md, .claude, and .product-strategy; add AGENTS.md

AGENTS.md

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+# Aether
+
+**Distributed event sourcing primitives for Go, powered by NATS.**
+
+---
+
+## Development Commands
+
+```bash
+make build    # go build ./...
+make test     # go test ./...
+make lint     # golangci-lint run
+make clean    # go clean
+```
+
+## NATS Server Requirement
+
+Integration tests require NATS with JetStream enabled:
+
+```bash
+brew install nats-server
+nats-server -js
+```
+
+Run tests in a separate terminal after starting NATS.
+
+## Project Structure
+
+```
+aether/
+├── event.go           # Event, ActorSnapshot, EventStore interface
+├── eventbus.go        # EventBus, EventBroadcaster interface
+├── nats_eventbus.go   # NATSEventBus implementation
+├── metrics*.go        # Prometheus metrics
+├── store/             # EventStore implementations
+│   ├── memory.go      # InMemoryEventStore (testing)
+│   └── jetstream.go   # JetStreamEventStore (production)
+├── cluster/           # Cluster management
+│   ├── manager.go     # ClusterManager
+│   ├── discovery.go   # NodeDiscovery
+│   ├── hashring.go    # ConsistentHashRing
+│   ├── shard.go       # ShardManager
+│   ├── leader.go      # LeaderElection
+│   └── types.go       # Cluster types
+├── examples/          # Usage examples
+└── eventstorming/     # Domain modeling reference
+```
+
+## Core Patterns
+
+### Event Versioning
+
+Events for each actor must have monotonically increasing versions:
+
+```go
+currentVersion, _ := store.GetLatestVersion(actorID)
+event := &aether.Event{
+    ActorID:   actorID,
+    Version:   currentVersion + 1,
+    // ...
+}
+err := store.SaveEvent(event)
+if errors.Is(err, aether.ErrVersionConflict) {
+    // Reload and retry
+}
+```
+
+### Namespace Isolation
+
+Namespaces provide logical boundaries for events:
+
+```go
+// Event bus namespace
+ch := eventBus.Subscribe("tenant-abc")
+eventBus.Publish("tenant-abc", event)
+
+// Store namespace
+store, _ := store.NewJetStreamEventStoreWithNamespace(natsConn, "events", "tenant-abc")
+```
+
+Namespaces sanitize special characters and prefix stream names for complete data isolation.
+
+### JetStream Cache Behavior
+
+`JetStreamEventStore` caches actor versions for performance. Cache is invalidated when `GetLatestVersion` detects a newer version from external writes.
+
+## Testing
+
+- Unit tests: `go test -v ./...`
+- Single test: `go test -v -run TestName`
+- Single file: `go test -v ./store/...`
+- Benchmarks: `go test -bench=. -benchmem`
+
+Integration tests require running NATS server first.
+
+## Linting
+
+```bash
+golangci-lint run
+golangci-lint run --fix
+```
+
+## References
+
+- [vision.md](./vision.md) - Product vision and principles
+- [examples/README.md](./examples/README.md) - Example patterns