feat(2meet-data-optimizer): backfill writes made while the Hook Bus was off

- When an entity goes from disabled to dual_write / shadow_read, or the Hook Bus flag is switched on, a single WP-Cron event (tmdo_drift_resync, one per entity, 60 s later) runs drift-check --fix for the entities that keep native meta, so values written while flat was bypassed land in flat. aeav_only is never touched.
- A full fix instead of the planned post_modified_gmt increment (decision 2026-09-27): meta-only writes such as WooCommerce's direct stock SQL do not bump post_modified. No wpdo_bridge_off_since.
- The resync hook is cleared on deactivate / uninstall (literal name: uninstall.php does not load TMDO_Drift_Check).
- Verify: DriftCheckTest resync cases (RED before); dev36 end to end with real WP-Cron: write while user disabled → miss 1 → bridge-mode user dual_write schedules tmdo_drift_resync [user] → run → drift 0.
- PR: PR-074

includes/diagnostic/class-tmdo-drift-check.php

@@ -45,6 +45,18 @@ final class TMDO_Drift_Check {
 	 */
 	public const CRON_SAMPLE = 500;
 
+	/**
+	 * Single WP-Cron event rebuilding an entity's flat tables from native after
+	 * writes bypassed them. Argument: the entity type.
+	 */
+	public const RESYNC_HOOK = 'tmdo_drift_resync';
+
+	/**
+	 * Seconds before the scheduled rebuild, so the switch that triggered it
+	 * finishes first.
+	 */
+	private const RESYNC_DELAY = 60;
+
 	/**
 	 * MySQL regex for a plain decimal number, used to skip rows that obviously match.
 	 * Exact matches compare BINARY: meta and flat tables may differ in collation,
@@ -122,6 +134,118 @@ final class TMDO_Drift_Check {
 		}
 	}
 
+	/**
+	 * Entities to rebuild after a mode change: one whose flat tables were not
+	 * written (disabled) is written next to native again, and values written
+	 * meanwhile are missing from flat.
+	 *
+	 * @param string $entity_type Entity type.
+	 * @param string $new_mode    New mode.
+	 * @param string $old_mode    Previous mode.
+	 * @return string[]
+	 */
+	public static function resync_after_mode_change( string $entity_type, string $new_mode, string $old_mode ): array {
+		$keeps_native = array( TMDO_Mode_Manager::MODE_DUAL_WRITE, TMDO_Mode_Manager::MODE_SHADOW_READ );
+		return TMDO_Mode_Manager::MODE_DISABLED === $old_mode && in_array( $new_mode, $keeps_native, true ) ? array( $entity_type ) : array();
+	}
+
+	/**
+	 * Entities to rebuild after the Hook Bus flag changes: no write reached
+	 * flat while it was off. Every entity written to both native and flat
+	 * (aeav_only keeps flat as the source of truth).
+	 *
+	 * @param mixed $old_value Previous flag value.
+	 * @param mixed $value     New flag value.
+	 * @return string[]
+	 */
+	public static function resync_after_hook_bus_change( $old_value, $value ): array {
+		if ( self::flag_on( $old_value ) || ! self::flag_on( $value ) ) {
+			return array();
+		}
+		$entities = array();
+		foreach ( TMDO_Entity_Registry::VALID_ENTITY_TYPES as $entity_type ) {
+			if ( TMDO_Mode_Manager::writes_to_flat( $entity_type ) && TMDO_Mode_Manager::writes_to_eav( $entity_type ) ) {
+				$entities[] = $entity_type;
+			}
+		}
+		return $entities;
+	}
+
+	/**
+	 * `wpdo_bridge_mode_changed` handler.
+	 *
+	 * @param string $entity_type Entity type.
+	 * @param string $new_mode    New mode.
+	 * @param string $old_mode    Previous mode.
+	 */
+	public static function on_mode_changed( string $entity_type, string $new_mode, string $old_mode ): void {
+		self::schedule_resync( self::resync_after_mode_change( $entity_type, $new_mode, $old_mode ) );
+	}
+
+	/**
+	 * `update_option_wpdo_hook_bus_enabled` handler.
+	 *
+	 * @param mixed $old_value Previous flag value.
+	 * @param mixed $value     New flag value.
+	 */
+	public static function on_hook_bus_toggled( $old_value, $value ): void {
+		self::schedule_resync( self::resync_after_hook_bus_change( $old_value, $value ) );
+	}
+
+	/**
+	 * `add_option_wpdo_hook_bus_enabled` handler: the flag is stored for the first time.
+	 *
+	 * @param string $option Option name.
+	 * @param mixed  $value  Flag value.
+	 */
+	public static function on_hook_bus_added( $option, $value ): void {
+		unset( $option );
+		self::schedule_resync( self::resync_after_hook_bus_change( '0', $value ) );
+	}
+
+	/**
+	 * RESYNC_HOOK handler. An entity that has meanwhile moved to aeav_only is
+	 * left alone (fix() refuses).
+	 *
+	 * @param string $entity_type Entity type.
+	 */
+	public static function run_scheduled_fix( string $entity_type ): void {
+		try {
+			$result = self::fix( $entity_type );
+			TMDO_Logger::info( 'drift_resync', array( 'entity' => $entity_type ) + $result['fixed'] );
+		} catch ( InvalidArgumentException | RuntimeException $e ) {
+			TMDO_Logger::info(
+				'drift_resync_skipped',
+				array(
+					'entity' => $entity_type,
+					'reason' => $e->getMessage(),
+				)
+			);
+		}
+	}
+
+	/**
+	 * Schedule one rebuild per entity type (not twice while one is pending).
+	 *
+	 * @param string[] $entities Entity types.
+	 */
+	private static function schedule_resync( array $entities ): void {
+		foreach ( $entities as $entity_type ) {
+			if ( ! wp_next_scheduled( self::RESYNC_HOOK, array( $entity_type ) ) ) {
+				wp_schedule_single_event( time() + self::RESYNC_DELAY, self::RESYNC_HOOK, array( $entity_type ) );
+			}
+		}
+	}
+
+	/**
+	 * Whether a stored Hook Bus flag value means "on" (as TMDO_Hook_Bus_Bridge reads it).
+	 *
+	 * @param mixed $value Flag value.
+	 */
+	private static function flag_on( $value ): bool {
+		return '1' === (string) $value || true === $value;
+	}
+
 	/**
 	 * Rebuild drifted flat rows from native meta, then check again.
 	 *