Add an in-process post event bus (#13)

Handlers emit PostCreated and PostUpdated after a successful write. Store writes do not publish, and hidden roots are skipped.

Reviewed-on: #13
Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/events/recording.go

@@ -0,0 +1,44 @@
+package events
+
+import (
+	"context"
+	"sync"
+)
+
+// Recording is a test Publisher that records events synchronously.
+type Recording struct {
+	mu  sync.Mutex
+	evs []any
+}
+
+// Publish appends ev.
+func (r *Recording) Publish(_ context.Context, ev any) {
+	if r == nil {
+		return
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.evs = append(r.evs, ev)
+}
+
+// Len returns the number of recorded events.
+func (r *Recording) Len() int {
+	if r == nil {
+		return 0
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	return len(r.evs)
+}
+
+// Snapshot returns a copy of recorded events.
+func (r *Recording) Snapshot() []any {
+	if r == nil {
+		return nil
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	out := make([]any, len(r.evs))
+	copy(out, r.evs)
+	return out
+}