feat: add session indicators and top exec commands to dashboard

Add visual indicators to session tables (replay badge when events exist,
exec badge for exec sessions) and a new "Top Exec Commands" table on the
dashboard. Includes EventCount field on Session, GetTopExecCommands on
Store interface, and truncateCommand template function.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/web/web_test.go

@@ -340,6 +340,61 @@ func TestMetricsBearerToken(t *testing.T) {
 	})
 }
 
+func TestTruncateCommand(t *testing.T) {
+	funcMap := templateFuncMap()
+	fn := funcMap["truncateCommand"].(func(string) string)
+
+	tests := []struct {
+		input string
+		want  string
+	}{
+		{"short", "short"},
+		{"exactly fifty characters long! that is what it i.", "exactly fifty characters long! that is what it i."},
+		{"this string is definitely longer than fifty characters and should be truncated", "this string is definitely longer than fifty charac..."},
+		{"", ""},
+	}
+
+	for _, tt := range tests {
+		got := fn(tt.input)
+		if got != tt.want {
+			t.Errorf("truncateCommand(%q) = %q, want %q", tt.input, got, tt.want)
+		}
+	}
+}
+
+func TestDashboardExecCommands(t *testing.T) {
+	store := storage.NewMemoryStore()
+	ctx := context.Background()
+
+	id, err := store.CreateSession(ctx, "10.0.0.1", "root", "bash", "")
+	if err != nil {
+		t.Fatalf("creating session: %v", err)
+	}
+	if err := store.SetExecCommand(ctx, id, "uname -a"); err != nil {
+		t.Fatalf("setting exec command: %v", err)
+	}
+
+	srv, err := NewServer(store, slog.Default(), nil, "")
+	if err != nil {
+		t.Fatalf("NewServer: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	w := httptest.NewRecorder()
+	srv.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("status = %d, want 200", w.Code)
+	}
+	body := w.Body.String()
+	if !strings.Contains(body, "Top Exec Commands") {
+		t.Error("response should contain 'Top Exec Commands'")
+	}
+	if !strings.Contains(body, "uname -a") {
+		t.Error("response should contain exec command 'uname -a'")
+	}
+}
+
 func TestStaticAssets(t *testing.T) {
 	srv := newTestServer(t)