test: fill remaining V1 test coverage

Add JSONB, pointer/filter, MustFetchOne, and dialect logger registration
tests for dbxm and dbxp.

Co-authored-by: Cursor <cursoragent@cursor.com>

ptr_test.go

@@ -0,0 +1,26 @@
+package dbx
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPtr_Val(t *testing.T) {
+	assert.Nil(t, Ptr(""))
+	assert.Equal(t, Ptr("hi"), Ptr("hi"))
+	assert.Equal(t, "", Val((*string)(nil)))
+	assert.Equal(t, "hi", Val(Ptr("hi")))
+}
+
+func TestStringToFilter(t *testing.T) {
+	assert.Equal(t, "%hello%world%", StringToFilter("hello world"))
+	assert.Equal(t, "%test%", StringToFilter("%test%"))
+}
+
+func TestTrimPtr(t *testing.T) {
+	s := "  hello  "
+	assert.Equal(t, "hello", *TrimPtr(&s))
+	assert.Nil(t, TrimPtr(nil))
+	assert.Nil(t, TrimPtrToNil(Ptr("   ")))
+}