perf(2meet-data-optimizer): key the routed count cache on the SQL without wpdb's placeholder escape

- keyword searches carry wpdb's placeholder escape for "%" ({<hash>}), which
  is new in every request, so md5(count SQL) never matched across requests
  and every keyword search recounted (the 2.2 "keyword + filter routed slower
  than native" finding). The key now uses remove_placeholder_escape()
- found in the 2.3 acceptance: dev36 keyword + price routed 6.2 s vs native
  4.9 s; PR-091's in-process check reused one process, one escape
- Verify: PostQueryRouterFoundRowsTest (two escapes, one COUNT), integration
  588, unit 703, phpcs, stan; dev36 front-end
- PR: PR-116 (2.3 acceptance)

tests/integration/PostQueryRouterFoundRowsTest.php

@@ -157,6 +157,49 @@ class PostQueryRouterFoundRowsTest extends TestCase {
 		$this->assertSame( '0', $count( '2' ), 'recounted' );
 	}
 
+	/**
+	 * Keyword searches carry wpdb's placeholder escape for "%", which changes
+	 * with every request: the cache key uses the SQL without it, or no search
+	 * with a keyword ever hits the cached count.
+	 */
+	public function test_the_cached_count_survives_a_new_placeholder_escape(): void {
+		global $wpdb;
+		$real = $wpdb;
+		$wpdb = new class( $real ) {
+			public int $counts = 0;
+
+			public function __construct( private object $db ) {}
+
+			public function remove_placeholder_escape( string $sql ): string {
+				return (string) preg_replace( '/\{[0-9a-f]{8}\}/', '%', $sql );
+			}
+
+			public function __call( string $name, array $args ) {
+				if ( 'get_var' === $name && str_contains( (string) $args[0], 'COUNT(*)' ) ) {
+					++$this->counts;
+				}
+				return $this->db->$name( ...$args );
+			}
+
+			public function __get( string $name ) {
+				return $this->db->$name;
+			}
+		};
+		try {
+			foreach ( array( '{1a2b3c4d}', '{9f8e7d6c}' ) as $escape ) { // Two requests.
+				list( $router, $query, $request ) = $this->routed();
+				$request = str_replace( ' GROUP BY', " AND '{$escape}' = '{$escape}' GROUP BY", $request );
+				$router->posts_request( $request, $query );
+				$this->assertSame( '2', $real->get_var( $router->found_posts_query( 'SELECT FOUND_ROWS()', $query ) ) );
+			}
+			$counts = $wpdb->counts;
+		} finally {
+			$wpdb = $real;
+		}
+
+		$this->assertSame( 1, $counts, 'counted once' );
+	}
+
 	public function test_flat_writes_and_deletes_move_posts_last_changed(): void {
 		$GLOBALS['_wp_current_filter'] = 'update_post_metadata';
 		$before                        = wp_cache_get_last_changed( 'posts' );