sqlexec: cover the HandleSQLPattern regex path over HTTP

Add an HTTP test that registers a regex matcher and echoes back a captured
submatch, exercising Server.HandleSQLPattern and Request.Match end-to-end. This
was the only SQL-exec path without coverage; it also gives HandleSQLPattern a
caller (the deadcode check flagged the Server-level wrapper as unreachable).

Co-authored-by: Isaac

Author: pietern

libs/sqlexec/sqlexec_http_test.go

@@ -1,6 +1,7 @@
 package sqlexec_test
 
 import (
+	"regexp"
 	"testing"
 	"time"
 
@@ -48,6 +49,19 @@ func TestHTTPExecuteSuccess(t *testing.T) {
 	assert.Equal(t, [][]string{{"1", "2"}}, r.Rows)
 }
 
+func TestHTTPExecutePattern(t *testing.T) {
+	server := newServer(t)
+	// A regex matcher echoes back a captured submatch, exercising the
+	// HandleSQLPattern path and Request.Match over the full HTTP round-trip.
+	server.HandleSQLPattern(regexp.MustCompile(`^SELECT (\d+)$`), func(r testsql.Request) testsql.Result {
+		return testsql.Result{Columns: []string{"n"}, Rows: [][]string{{r.Match[1]}}}
+	})
+
+	got, err := httpClient(t, server).ExecuteScalar(t.Context(), "SELECT 42")
+	require.NoError(t, err)
+	assert.Equal(t, "42", got)
+}
+
 func TestHTTPExecutePolls(t *testing.T) {
 	server := newServer(t)
 	server.HandleSQL("SELECT 1", func(testsql.Request) testsql.Result {