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/class-tmdo-hook-bus-bridge.php

@@ -54,7 +54,7 @@ final class TMDO_Hook_Bus_Bridge {
 		if ( null !== self::$cache ) {
 			return self::$cache;
 		}
-		$value       = get_option( self::OPTION, '1' );  // Default ON as of v2.5.4.
+		$value       = get_option( self::OPTION, '0' );
 		self::$cache = ( '1' === (string) $value || true === $value );
 		return self::$cache;
 	}