feat(ui): Structured observability/status view (#40)

* refactor(ui): Make message status SSE name more specific

Signed-off-by: Richard Palethorpe <io@richiejp.com>

* feat(ui): Add structured observability events

Signed-off-by: Richard Palethorpe <io@richiejp.com>

---------

Signed-off-by: Richard Palethorpe <io@richiejp.com>

core/agent/observer.go

@@ -0,0 +1,87 @@
+package agent
+
+import (
+	"encoding/json"
+	"sync"
+	"sync/atomic"
+
+	"github.com/mudler/LocalAGI/core/sse"
+	"github.com/mudler/LocalAGI/core/types"
+	"github.com/mudler/LocalAGI/pkg/xlog"
+)
+
+type Observer interface {
+	NewObservable() *types.Observable
+	Update(types.Observable)
+	History() []types.Observable
+}
+
+type SSEObserver struct {
+	agent   string
+	maxID   int32
+	manager sse.Manager
+
+	mutex sync.Mutex
+	history []types.Observable
+	historyLast int
+}
+
+func NewSSEObserver(agent string, manager sse.Manager) *SSEObserver {
+	return &SSEObserver{
+		agent:   agent,
+		maxID:   1,
+		manager: manager,
+		history: make([]types.Observable, 100),
+	}
+}
+
+func (s *SSEObserver) NewObservable() *types.Observable {
+	id := atomic.AddInt32(&s.maxID, 1)
+	return &types.Observable{
+		ID:    id - 1,
+		Agent: s.agent,
+	}
+}
+
+func (s *SSEObserver) Update(obs types.Observable) {
+	data, err := json.Marshal(obs)
+	if err != nil {
+		xlog.Error("Error marshaling observable", "error", err)
+		return
+	}
+	msg := sse.NewMessage(string(data)).WithEvent("observable_update")
+	s.manager.Send(msg)
+
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	for i, o := range s.history {
+		if o.ID == obs.ID {
+			s.history[i] = obs
+			return
+		}
+	}
+
+	s.history[s.historyLast] = obs
+	s.historyLast += 1
+	if s.historyLast >= len(s.history) {
+		s.historyLast = 0
+	}
+}
+
+func (s *SSEObserver) History() []types.Observable {
+	h := make([]types.Observable, 0, 20)
+
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	for _, obs := range s.history {
+		if obs.ID == 0 {
+			continue
+		}
+
+		h = append(h, obs)
+	}
+
+	return h
+}