Export parser AST types from the alasql module declaration

[assapir]

Closes the follow-up in #2498 (comment).

Problem

v4.19.0 added the parser AST interfaces, but consumers can't name them:

import type {Statement} from 'alasql';        // TS2305
import alasql = require('alasql');
let a: alasql.AlaSQLAST;                      // TS2503
export function p(sql: string) {
	return alasql.parse(sql);                 // TS4058
}

In an ambient module declaration, all declarations are implicitly exported unless the module contains an export assignment. export = alasql is that assignment, so nothing but the const escaped.

Fix

export on the top-level declarations inside declare module 'alasql'. Type-only, no bodies moved, export = kept — so the module stays callable.

Verification

A consumer file compiled with tsc --strict --declaration, before vs. after:

	before	after
import type {Statement, AlaSQLAST}	TS2305 ×2	ok
import a = require('alasql'); a.AlaSQLAST	TS2503	ok
import * as a; a.AlaSQLAST	TS2503	ok
exported fn returning parse()	TS4058	ok
import alasql from 'alasql' + call / .options / .fn	ok	ok