v4 architecture: pipeline stages, SDK, event bus, LLM-driven memory consolidation

- SDK PluginAPI (internal/plugin/sdk/): RegisterTool/RegisterStage/Subscribe/Publish
- EventBus (internal/events/): system-level pub/sub with wildcard support
- StageHost (internal/agent/core/stages.go): 7-stage message pipeline
- Agent core: on_input/pre_action/post_action/before_toolcall/after_toolcall/before_output/after_output
- Plugin Registry: SDK plugin registration and tool routing
- GraphDB.MergeEntities: entity consolidation with relation redirection
- memory_merge tool: allows LLM to merge similar entities
- Consolidation task: heartbeat detects conflicts, enqueues via IO for LLM decision
- _consolidation_ internal channel for system-level memory maintenance
- Comprehensive documentation: ARCHITECTURE.md, PLAN.md, DESIGN.md, README.md
- 54 tests across all packages, all passing

internal/events/bus_test.go

@@ -0,0 +1,102 @@
+package events
+
+import (
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestBusPublishSubscribe(t *testing.T) {
+	bus := NewBus()
+	var count int32
+
+	bus.Subscribe(EventRawInput, func(evt *Event) {
+		atomic.AddInt32(&count, 1)
+	})
+
+	bus.Publish(&Event{
+		Type:    EventRawInput,
+		Source:  "test",
+		Payload: map[string]interface{}{"content": "hello"},
+	})
+
+	if c := atomic.LoadInt32(&count); c != 1 {
+		t.Errorf("expected 1, got %d", c)
+	}
+}
+
+func TestBusWildcard(t *testing.T) {
+	bus := NewBus()
+	var count int32
+
+	bus.Subscribe(EventAll, func(evt *Event) {
+		atomic.AddInt32(&count, 1)
+	})
+
+	bus.Publish(&Event{Type: EventRawInput, Source: "test"})
+	bus.Publish(&Event{Type: EventToolCall, Source: "test"})
+
+	if c := atomic.LoadInt32(&count); c != 2 {
+		t.Errorf("expected 2, got %d", c)
+	}
+}
+
+func TestBusUnsubscribe(t *testing.T) {
+	bus := NewBus()
+	var count int32
+
+	handler := func(evt *Event) {
+		atomic.AddInt32(&count, 1)
+	}
+	unsub := bus.Subscribe(EventRawInput, handler)
+
+	bus.Publish(&Event{Type: EventRawInput, Source: "test"})
+	unsub()
+	bus.Publish(&Event{Type: EventRawInput, Source: "test"})
+
+	if c := atomic.LoadInt32(&count); c != 1 {
+		t.Errorf("expected 1 after unsub, got %d", c)
+	}
+}
+
+func TestBusNoMatch(t *testing.T) {
+	bus := NewBus()
+	var count int32
+
+	bus.Subscribe(EventRawInput, func(evt *Event) {
+		atomic.AddInt32(&count, 1)
+	})
+
+	bus.Publish(&Event{Type: EventAgentOutput, Source: "test"})
+
+	if c := atomic.LoadInt32(&count); c != 0 {
+		t.Errorf("expected 0, got %d", c)
+	}
+}
+
+func TestBusConcurrent(t *testing.T) {
+	bus := NewBus()
+	var count int32
+
+	bus.Subscribe(EventAll, func(evt *Event) {
+		atomic.AddInt32(&count, 1)
+	})
+
+	done := make(chan struct{})
+	go func() {
+		for i := 0; i < 100; i++ {
+			bus.Publish(&Event{Type: EventRawInput, Source: "test"})
+		}
+		close(done)
+	}()
+
+	select {
+	case <-done:
+	case <-time.After(3 * time.Second):
+		t.Fatal("timeout")
+	}
+
+	if c := atomic.LoadInt32(&count); c != 100 {
+		t.Errorf("expected 100, got %d", c)
+	}
+}