fix(2meet-data-optimizer): serve native meta in shadow_read and compare flat values

- In shadow_read, TMDO_Hook_Bus::intercept_get() returned the flat value.
  update_metadata() reads the old value through that filter after the Hook
  Bus has upserted the new one, so WP saw old === new and never wrote native
  meta: every update in shadow_read was lost on demotion (dev36 2026-09-26).
  shadow_read now returns $check (native) and compares flat on a sample of
  reads (filter tmdo_shadow_compare_sample_rate, default 0.1). aeav_only is
  unchanged; the post query router still routes in shadow_read.
- Live suite shadow_write: xfail markers removed, HivePress listing case
  added (new int key hp_rating_count); fixtures gain post() and a
  post_type-scoped field()/flat().
- Verify: live shadow_write + serialized 8/8 PASS (old code: 4 FAIL);
  unit 685 OK, integration 484 OK, phpcs (phpcs.xml) 0, stan OK
- PR: PR-056

includes/engine/class-tmdo-hook-bus.php

@@ -388,12 +388,20 @@ final class TMDO_Hook_Bus {
 		// ── Mode-aware dispatch ──────────────────────────────
 		// disabled    : 完全不攔截,回傳 $check 讓 WP 走原生 EAV
 		// dual_write  : 讀取仍走 EAV(flat 可能還沒有資料),回傳 $check
-		// shadow_read : 讀取走 UAE flat,同時與 EAV 比對記錄 diff
+		// shadow_read : 讀取仍走 EAV,抽樣與 flat 比對記錄 diff
 		// aeav_only   : 讀取走 UAE flat,不讀 EAV
 		if ( ! TMDO_Mode_Manager::reads_from_flat( $type ) ) {
 			return $check;  // disabled / dual_write
 		}
 
+		// shadow_read serves native: update_metadata() reads the old value
+		// through this filter, and serving the just-upserted flat value made
+		// WP see old === new and skip the native write (dev36, 2026-09-26).
+		if ( TMDO_Mode_Manager::does_shadow_compare( $type ) ) {
+			self::maybe_shadow_compare( $type, (int) $object_id, $meta_key, $field_def );
+			return $check;
+		}
+
 		$group = $field_def['group'];
 		$row   = self::get_or_load_row( $type, (int) $object_id, $group );
 
@@ -401,22 +409,6 @@ final class TMDO_Hook_Bus {
 		$has_value = is_array( $row ) && array_key_exists( $col, $row );
 		$value     = $has_value ? TMDO_Type_Caster::from_db( $row[ $col ], $field_def ) : null;
 
-		// Shadow-read:與 EAV 比對,記錄差異
-		if ( TMDO_Mode_Manager::does_shadow_compare( $type ) ) {
-			try {
-				TMDO_Shadow_Diff_Logger::compare_and_log(
-					$type,
-					(int) $object_id,
-					$meta_key,
-					$value,
-					$field_def
-				);
-			} catch ( \Throwable $e ) {
-				// 比對失敗不該影響讀取
-				TMDO_Logger::error( 'entity_bridge', 'shadow_compare_exception', $e->getMessage() );
-			}
-		}
-
 		// 值為空 → 回 WP 原生慣例
 		if ( empty( $row ) || $value === null || $value === '' ) {
 			return $single ? '' : array();
@@ -426,6 +418,36 @@ final class TMDO_Hook_Bus {
 		return $single ? array( $value ) : array( $value );
 	}
 
+	/**
+	 * shadow_read: compare the flat value with native meta for a sample of reads.
+	 *
+	 * Each compare costs a flat row read and a native SQL read, so only a share
+	 * of reads is checked (filter `tmdo_shadow_compare_sample_rate`, 0..1,
+	 * default 0.1). The logger rate-limits repeated diffs itself.
+	 *
+	 * @param string               $type      Entity type.
+	 * @param int                  $object_id Entity ID.
+	 * @param string               $meta_key  Meta key.
+	 * @param array<string, mixed> $field_def Field definition.
+	 */
+	private static function maybe_shadow_compare( string $type, int $object_id, string $meta_key, array $field_def ): void {
+		$rate = (float) apply_filters( 'tmdo_shadow_compare_sample_rate', 0.1, $type, $meta_key );
+		if ( $rate <= 0 || ( $rate < 1 && wp_rand( 1, 1000 ) > $rate * 1000 ) ) {
+			return;
+		}
+
+		$row   = self::get_or_load_row( $type, $object_id, $field_def['group'] );
+		$col   = TMDO_Schema_Manager::sanitize_column_name( $meta_key );
+		$value = array_key_exists( $col, $row ) ? TMDO_Type_Caster::from_db( $row[ $col ], $field_def ) : null;
+
+		try {
+			TMDO_Shadow_Diff_Logger::compare_and_log( $type, $object_id, $meta_key, $value, $field_def );
+		} catch ( \Throwable $e ) {
+			// 比對失敗不該影響讀取
+			TMDO_Logger::error( 'entity_bridge', 'shadow_compare_exception', $e->getMessage() );
+		}
+	}
+
 	/**
 	 * 取得（或載入）完整列資料，並快取
 	 */