Slice 3: activity feed and active project (SSE + MCP tools)

Add internal/activity (thread-safe active project + bounded event feed with subscriber fan-out). Service exposes active-project/activity methods and takes the feed. New MCP tools get_active_project/set_active_project/get_activity and HTTP endpoints GET/POST /api/active-project, /api/activity, and /events (SSE). New <activity-feed> component updates live via EventSource; <repo-list> sets the active project on selection. Verified end-to-end in the running app: user actions push live events and set the active project (actor=user), all readable by Claude over MCP.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/mcp/mcp_test.go

@@ -13,6 +13,7 @@ import (
 
 	mcpsdk "github.com/modelcontextprotocol/go-sdk/mcp"
 
+	"gitmanager/internal/activity"
 	"gitmanager/internal/git"
 	"gitmanager/internal/repos"
 	"gitmanager/internal/service"
@@ -41,7 +42,7 @@ func TestMCPRoundTrip(t *testing.T) {
 	scanner := repos.NewScanner(g, log, []string{root}, 3, nil, time.Minute, false)
 	scanner.Refresh(context.Background())
 
-	svc := service.New(g, scanner.Index)
+	svc := service.New(g, scanner.Index, activity.New(log, 200))
 	srv := NewServer(svc, "test")
 
 	// Wire an in-memory client<->server session.
@@ -100,6 +101,64 @@ func TestMCPRoundTrip(t *testing.T) {
 	if !res.IsError {
 		t.Fatalf("expected IsError for unknown repo, got success")
 	}
+
+	// active project starts empty.
+	res, err = cs.CallTool(ctx, &mcpsdk.CallToolParams{Name: "get_active_project"})
+	if err != nil {
+		t.Fatalf("get_active_project: %v", err)
+	}
+	var ap struct {
+		Path string `json:"path"`
+	}
+	decodeResult(t, res, &ap)
+	if ap.Path != "" {
+		t.Fatalf("expected empty active project, got %q", ap.Path)
+	}
+
+	// set_active_project to our repo, then read it back.
+	res, err = cs.CallTool(ctx, &mcpsdk.CallToolParams{
+		Name:      "set_active_project",
+		Arguments: map[string]any{"path": states[0].Path},
+	})
+	if err != nil {
+		t.Fatalf("set_active_project: %v", err)
+	}
+	if res.IsError {
+		t.Fatalf("set_active_project returned tool error: %+v", res.Content)
+	}
+	res, _ = cs.CallTool(ctx, &mcpsdk.CallToolParams{Name: "get_active_project"})
+	decodeResult(t, res, &ap)
+	if ap.Path != states[0].Path {
+		t.Fatalf("active project = %q, want %q", ap.Path, states[0].Path)
+	}
+
+	// setting an unknown project is a tool error.
+	res, err = cs.CallTool(ctx, &mcpsdk.CallToolParams{
+		Name:      "set_active_project",
+		Arguments: map[string]any{"path": filepath.Join(root, "nope")},
+	})
+	if err != nil {
+		t.Fatalf("set_active_project(bad) protocol error: %v", err)
+	}
+	if !res.IsError {
+		t.Fatalf("expected IsError for unknown active project")
+	}
+
+	// the activity feed should now contain the active-project-changed event.
+	res, _ = cs.CallTool(ctx, &mcpsdk.CallToolParams{Name: "get_activity"})
+	var act struct {
+		Events []activity.Event `json:"events"`
+	}
+	decodeResult(t, res, &act)
+	found := false
+	for _, ev := range act.Events {
+		if ev.Kind == "active-project-changed" && ev.Repo == states[0].Path && ev.Actor == activity.ActorClaude {
+			found = true
+		}
+	}
+	if !found {
+		t.Fatalf("expected an active-project-changed event by claude, got %+v", act.Events)
+	}
 }
 
 // decodeResult unmarshals the JSON text content of a tool result into v.