fix(workspace-server): check rows.Err() after iteration in MemoryHandler.List

The List handler iterated over rows.Next() but never checked rows.Err()
after the loop. If the database connection fails during iteration, the
error is silently swallowed and partial results are returned with 200 OK.

Add a rows.Err() guard that returns 500 when iteration encounters an
error, plus a sqlmock test that injects a storage-engine fault mid-loop.

Tracked: rows.Err() audit gap (follow-up to internal#348 / PR #1743).

workspace-server/internal/handlers/memory.go

@@ -54,6 +54,11 @@ func (h *MemoryHandler) List(c *gin.Context) {
 		entry.Value = json.RawMessage(value)
 		entries = append(entries, entry)
 	}
+	if err := rows.Err(); err != nil {
+		log.Printf("Memory list iteration error: %v", err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "query iteration failed"})
+		return
+	}
 
 	c.JSON(http.StatusOK, entries)
 }

workspace-server/internal/handlers/memory_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"database/sql"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -74,6 +75,34 @@ func TestMemoryList_DBError(t *testing.T) {
 	}
 }
 
+// TestMemoryList_RowsErr_Returns500 verifies that a rows.Err() set during
+// iteration causes the handler to return 500 rather than partial results.
+func TestMemoryList_RowsErr_Returns500(t *testing.T) {
+	mock := setupTestDB(t)
+	setupTestRedis(t)
+	handler := NewMemoryHandler()
+
+	cols := []string{"key", "value", "version", "expires_at", "updated_at"}
+	mock.ExpectQuery("SELECT key, value, version, expires_at, updated_at").
+		WithArgs("ws-rowerr").
+		WillReturnRows(sqlmock.NewRows(cols).
+			AddRow("ok-key", []byte(`"val"`), int64(1), nil, time.Now()).
+			RowError(0, errors.New("storage engine fault")))
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: "ws-rowerr"}}
+	c.Request = httptest.NewRequest("GET", "/workspaces/ws-rowerr/memory", nil)
+	handler.List(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("rows.Err() must yield 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet sqlmock expectations: %v", err)
+	}
+}
+
 // ==================== GET /workspaces/:id/memory/:key (Get) ====================
 
 func TestMemoryGet_Success(t *testing.T) {