Add Rust parser bridge helpers

When a native MySQL parser extension declares WP_MySQL_Native_Parser,
load a small bridge file that exposes WP_Parser_Grammar internals to the
extension. The native parser needs the grammar's terminal table, rules,
and lookahead map, but those live on a PHP object — the bridge function
hands them out as a plain array the extension can consume.

Author: adamziel

packages/mysql-on-sqlite/src/mysql/mysql-rust-bridge.php

@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * Bridge helpers for the optional Rust MySQL lexer/parser extension.
+ * PHP keeps the grammar object, while Rust owns the exported parser state.
+ */
+
+/**
+ * Export grammar internals for the native parser.
+ *
+ * @param WP_Parser_Grammar $grammar Parser grammar.
+ * @return array<string, mixed>
+ */
+function wp_sqlite_mysql_native_export_grammar( WP_Parser_Grammar $grammar ): array {
+	return array(
+		'highest_terminal_id'         => $grammar->highest_terminal_id,
+		'rules'                       => $grammar->rules,
+		'lookahead_is_match_possible' => $grammar->lookahead_is_match_possible,
+		'rule_names'                  => $grammar->rule_names,
+		'fragment_ids'                => $grammar->fragment_ids,
+	);
+}