fix(2meet-data-optimizer): skip cold-zone cache warming unless the cold module is active

- TMDO_Cache_Layer::prefetch() / warm_post() (and so on_save_post /
  on_loop_start) queried wp_wpdo_cold_{post_type} whenever cold fields
  were registered, even with the cold module idle and the table never
  created: every HivePress / WC save logged "table doesn't exist" errors.
  They now return unless the module is write-active and the table exists.
- CacheLayerTest activates the module in setUp; new cases assert zero cold
  queries while idle or when the table is missing.
- Verify: CacheLayerTest 12 OK; unit 671 OK, integration 480 OK,
  phpcs (phpcs.xml) 0, stan OK; dev36 live: seeding listings/products/
  vendors with cold_hp_listing idle → 0 wpdo_cold errors (was hundreds)
- PR: PR-054

includes/class-tmdo-cache-layer.php

@@ -40,7 +40,7 @@ class TMDO_Cache_Layer {
 		}
 
 		$cold_keys = TMDO_Schema_Registry::instance()->get_cold_meta_keys( $post_type );
-		if ( empty( $cold_keys ) ) {
+		if ( empty( $cold_keys ) || ! self::cold_active( $post_type ) ) {
 			return;
 		}
 
@@ -108,7 +108,7 @@ class TMDO_Cache_Layer {
 	 */
 	public static function warm_post( int $post_id, string $post_type ): void {
 		$cold_keys = TMDO_Schema_Registry::instance()->get_cold_meta_keys( $post_type );
-		if ( empty( $cold_keys ) ) {
+		if ( empty( $cold_keys ) || ! self::cold_active( $post_type ) ) {
 			return;
 		}
 
@@ -120,6 +120,19 @@ class TMDO_Cache_Layer {
 		TMDO_Zone_Cold::get_blob( $post_id, $post_type );
 	}
 
+	/**
+	 * Whether the cold zone holds data for this post type: its module writes
+	 * to the cold table and the table exists. Registered cold fields alone do
+	 * not mean either (zero side effect while the module is idle).
+	 *
+	 * @param string $post_type Post type.
+	 * @return bool
+	 */
+	private static function cold_active( string $post_type ): bool {
+		return TMDO_Feature_Flags::is_write_active( TMDO_Zone_Router::module_name( 'cold', $post_type ) )
+			&& TMDO_Schema_Manager::table_exists( TMDO_Zone_Cold::table( $post_type ) );
+	}
+
 	/**
 	 * Flush all cold cache for a post type.
 	 *

tests/unit/CacheLayerTest.php

@@ -11,17 +11,35 @@ class CacheLayerTest extends TestCase {
 	/** Rows returned by get_results() for the bulk-fetch query. */
 	public static array $db_rows = [];
 
+	/** Whether SHOW TABLES reports the cold table. */
+	public static bool $table_exists = true;
+
+	/** Queries that read the cold table (get_var / get_results on it). */
+	public static int $cold_queries = 0;
+
 	protected function setUp(): void {
 		self::$db_rows        = [];
+		self::$table_exists   = true;
+		self::$cold_queries   = 0;
 		$GLOBALS['_wp_cache'] = [];
 
 		// Reset Schema Registry singleton.
 		$ref = new ReflectionClass( WPDO_Schema_Registry::class );
 		$ref->getProperty( 'instance' )->setValue( null, null );
 
+		// The cold module is write-active unless a test says otherwise.
+		$this->set_cold_module( 'dual_write' );
+		WPDO_Schema_Manager::flush_table_exists_cache();
+
 		$this->setup_wpdb_mock();
 	}
 
+	private function set_cold_module( string $state ): void {
+		$GLOBALS['_wp_options']['wpdo_features'] = array( 'cold_hp_listing' => $state );
+		$prop = new ReflectionProperty( WPDO_Feature_Flags::class, 'cache' );
+		$prop->setValue( null, null );
+	}
+
 	private function setup_wpdb_mock(): void {
 		global $wpdb;
 
@@ -36,7 +54,15 @@ class CacheLayerTest extends TestCase {
 				}, $sql );
 			}
 
-			public function get_var( string $sql ): ?string { return null; }
+			public function get_var( string $sql ): ?string {
+				if ( preg_match( "/^SHOW TABLES LIKE '(.+)'$/", $sql, $m ) ) {
+					return CacheLayerTest::$table_exists ? stripslashes( $m[1] ) : null;
+				}
+				if ( str_contains( $sql, 'wpdo_cold_' ) ) {
+					++CacheLayerTest::$cold_queries;
+				}
+				return null;
+			}
 			public function get_row( string $sql, $output = OBJECT ) { return null; }
 			public function insert( string $table, array $data, $format = null ): int|false { return 1; }
 			public function update( string $table, array $data, array $where, $f = null, $wf = null ): int|false { return 1; }
@@ -44,11 +70,45 @@ class CacheLayerTest extends TestCase {
 			public function query( string $sql ): int|bool { return 1; }
 
 			public function get_results( string $sql, $output = OBJECT ): array {
+				if ( str_contains( $sql, 'wpdo_cold_' ) ) {
+					++CacheLayerTest::$cold_queries;
+				}
 				return CacheLayerTest::$db_rows;
 			}
 		};
 	}
 
+	// ── Zero side effect while the cold module is not active ─────────────────
+
+	public function test_prefetch_does_not_query_while_module_idle(): void {
+		$this->register_cold_field();
+		$this->set_cold_module( 'idle' );
+
+		WPDO_Cache_Layer::prefetch( [ 1, 2 ], 'hp_listing' );
+
+		$this->assertSame( 0, self::$cold_queries );
+		$this->assertEmpty( $GLOBALS['_wp_cache'] );
+	}
+
+	public function test_warm_post_does_not_query_while_module_idle(): void {
+		$this->register_cold_field();
+		$this->set_cold_module( 'idle' );
+
+		WPDO_Cache_Layer::warm_post( 20, 'hp_listing' );
+
+		$this->assertSame( 0, self::$cold_queries );
+	}
+
+	public function test_no_query_when_cold_table_is_missing(): void {
+		$this->register_cold_field();
+		self::$table_exists = false;
+
+		WPDO_Cache_Layer::prefetch( [ 1 ], 'hp_listing' );
+		WPDO_Cache_Layer::warm_post( 1, 'hp_listing' );
+
+		$this->assertSame( 0, self::$cold_queries );
+	}
+
 	// ── Helper: register cold field ──────────────────────────────────────────
 
 	private function register_cold_field( string $post_type = 'hp_listing', string $meta_key = 'hp_description' ): void {