refactor: replace pure TS scanner with WASM-based scanner from libpg-query

Replace the custom TypeScript comment scanner with PostgreSQL's real
lexer via libpg-query's WASM _wasm_scan function. This eliminates the
risk of bugs from reimplementing PostgreSQL's lexer in TypeScript.

Key changes:
- scanner.ts now loads the WASM module directly and calls _wasm_scan
  with proper JSON escaping (works around upstream bug where control
  characters in token text are not escaped)
- Dependency changed from libpg-query to @libpg-query/parser (full
  build with scan support)
- Unified loadModule() initializes both parse/deparse and scanner WASM
- All 36 tests passing including multi-line block comments and
  dollar-quoted string handling

Author: pyramation

packages/parse/__tests__/scanner.test.ts

@@ -1,6 +1,9 @@
-import { scanComments, ScannedElement } from '../src/scanner';
+import { scanComments, ScannedElement, initWasm } from '../src/scanner';
 
 describe('scanComments', () => {
+  beforeAll(async () => {
+    await initWasm();
+  });
   describe('line comments', () => {
     it('extracts a simple line comment', () => {
       const sql = '-- hello world\nSELECT 1;';

packages/parse/package.json

@@ -40,8 +40,8 @@
     "round-trip"
   ],
   "dependencies": {
+    "@libpg-query/parser": "^17.6.3",
     "@pgsql/types": "^17.6.2",
-    "libpg-query": "17.7.3",
     "pgsql-deparser": "workspace:*"
   },
   "devDependencies": {

packages/parse/src/index.ts

@@ -22,8 +22,14 @@ export { deparseEnhanced, deparseEnhancedSync, Deparser, DeparserOptions } from
 // Re-export standard deparse for non-enhanced use
 export { deparse, deparseSync } from 'pgsql-deparser';
 
-// Re-export loadModule from libpg-query
-export { loadModule } from 'libpg-query';
+// Unified loadModule that initializes both the library's WASM
+// (for parse/deparse) and our scanner's WASM (for _wasm_scan).
+import { loadModule as libLoadModule } from '@libpg-query/parser';
+import { initWasm } from './scanner';
+
+export async function loadModule(): Promise<void> {
+  await Promise.all([libLoadModule(), initWasm()]);
+}
 
 // Types
 export {

packages/parse/src/parse.ts

@@ -4,7 +4,7 @@
  * parse result's stmts array.
  */
 
-import { parse as libParse, parseSync as libParseSync } from 'libpg-query';
+import { parse as libParse, parseSync as libParseSync } from '@libpg-query/parser';
 import { ParseResult, RawStmt } from '@pgsql/types';
 import { scanComments, ScannedElement } from './scanner';
 import { EnhancedParseResult, EnhancedStmt } from './types';