fix(2meet-data-optimizer): stop auto-activating entity bridge on install

- install() no longer switches the Hook Bus on or puts user/term/comment
  into dual_write; the now-unused maybe_autoactivate_entity_bridge() is gone
- Hook Bus and Mode_Manager defaults are off/disabled; sites with stored
  modes (incl. aeav_only) keep them since only unset keys use defaults
- Guard run_dbdelta()'s upgrade.php require like install_v2_tables() so
  install() can run under the integration test stub

Verify: InstallerV2Test::test_install_does_not_enable_entity_bridge,
  ModeManagerDefaultsTest; unit 602 OK, integration 421 OK
PR: PR-007

includes/engine/class-tmdo-mode-manager.php

@@ -65,16 +65,15 @@ final class TMDO_Mode_Manager {
 	private static ?array $cache = null;
 
 	/**
-	 * 預設模式（v2.5.4 起）：
-	 *   post    → disabled（由 Legacy Feature_Flags FSM 管理，不由 Mode_Manager 控制）
-	 *   user / term / comment → dual_write（安全雙寫：寫入 flat table + 原生 EAV，讀取仍走 EAV）
+	 * 預設模式：全部 disabled，由管理者明確選擇後才啟用 entity bridge。
+	 * 已存在 wpdo_bridge_modes 的站台（包含 aeav_only）以儲存值為準，不受影響。
 	 */
 	private static function defaults(): array {
 		return array(
 			'post'    => self::MODE_DISABLED,
-			'user'    => self::MODE_DUAL_WRITE,
-			'term'    => self::MODE_DUAL_WRITE,
-			'comment' => self::MODE_DUAL_WRITE,
+			'user'    => self::MODE_DISABLED,
+			'term'    => self::MODE_DISABLED,
+			'comment' => self::MODE_DISABLED,
 		);
 	}