fix(schema): guard ClickHouse index loops against non-skip index types

Agent-Logs-Url: https://github.com/utopia-php/query/sessions/498037f0-05ae-40ad-8dfa-b72fe523705a

Co-authored-by: abnegate <5857008+abnegate@users.noreply.github.com>

Author: Copilot

src/Query/Schema/ClickHouse.php

@@ -125,6 +125,11 @@ public function compileAlter(Table $table): Statement
         }
 
         foreach ($table->indexes as $index) {
+            if ($index->type !== IndexType::Index) {
+                throw new UnsupportedException(
+                    'Only data-skipping indexes (index()) are supported in ClickHouse ALTER TABLE.'
+                );
+            }
             $alterations[] = 'ADD ' . $this->compileSkipIndex($index);
         }
 
@@ -176,6 +181,11 @@ public function compileCreate(Table $table, bool $ifNotExists = false): Statemen
         }
 
         foreach ($table->indexes as $index) {
+            if ($index->type !== IndexType::Index) {
+                throw new UnsupportedException(
+                    'Only data-skipping indexes (index()) are supported in ClickHouse CREATE TABLE.'
+                );
+            }
             $columnDefs[] = $this->compileSkipIndex($index);
         }