fix: keep TableExtractor table names as strings (#1794)

PHP coerces numeric-string array keys to ints, so collecting table names in
$tables[$name] and returning array_keys() can yield ints. That breaks the
declared list<string> and throws a TypeError in Recorder::linkTable(string).

Standard SQL like substring(x FROM 1 FOR 10) is enough to trigger it, since
the numeric operand matches the FROM pattern.

Closes #1793

Co-authored-by: Danny de Wit <d.dewit@fenceweb.com>

src/Plugins/Tia/TableExtractor.php

@@ -56,7 +56,7 @@ final class TableExtractor
             $tables[strtolower($name)] = true;
         }
 
-        $out = array_keys($tables);
+        $out = array_map(strval(...), array_keys($tables));
         sort($out);
 
         return $out;
@@ -112,7 +112,7 @@ final class TableExtractor
             }
         }
 
-        $out = array_keys($tables);
+        $out = array_map(strval(...), array_keys($tables));
         sort($out);
 
         return $out;