fix(migrations): support Closure-based 'up'/'down' in MigrationRunner

The runner was calling splitStatements(string) directly on migration['up']
without checking whether it was a Closure, causing a fatal type error on
all idempotent closure-based migrations (Phase_94_001, _002, Phase_96_001).
Now checks is_callable() first and invokes the closure, falling back to
string SQL splitting for plain-string migrations.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Core/Migration/MigrationRunner.php

@@ -38,13 +38,17 @@ final class MigrationRunner
 
                 if (is_array($migration) && isset($migration['up'])) {
                     $upSql = $migration['up'];
-                    $statements = $this->splitStatements($upSql);
+                    if (is_callable($upSql)) {
+                        $upSql($this->db);
+                    } else {
+                        $statements = $this->splitStatements((string) $upSql);
                         foreach ($statements as $stmt) {
                             $stmt = trim($stmt);
                             if ($stmt !== '') {
                                 $this->db->raw($stmt);
                             }
                         }
+                    }
                 } elseif (is_object($migration) && method_exists($migration, 'up')) {
                     $migration->up($this->db);
                 } elseif (is_callable($migration)) {
@@ -93,13 +97,18 @@ final class MigrationRunner
                     $migration = require $file;
 
                     if (is_array($migration) && isset($migration['down'])) {
-                        $statements = $this->splitStatements($migration['down']);
+                        $downSql = $migration['down'];
+                        if (is_callable($downSql)) {
+                            $downSql($this->db);
+                        } else {
+                            $statements = $this->splitStatements((string) $downSql);
                             foreach ($statements as $stmt) {
                                 $stmt = trim($stmt);
                                 if ($stmt !== '') {
                                     $this->db->raw($stmt);
                                 }
                             }
+                        }
                     } elseif (is_object($migration) && method_exists($migration, 'down')) {
                         $migration->down($this->db);
                     }