feat: implement @objectql/driver-pg-wasm package

Implement PostgreSQL WASM driver for browser environments following Q1 Phase 2 work plan.

Package features:
- Composition pattern wrapping SqlDriver for query compilation
- Custom Knex client adapter for PGlite WASM
- IndexedDB/OPFS/Memory persistence backends with auto-fallback
- Environment detection with ObjectQLError for missing WASM
- PostgreSQL-specific features: JSONB operators, full-text search
- Full transaction support with savepoints and isolation levels
- Comprehensive test suite (23 tests passing)

Implementation follows same patterns as @objectql/driver-sqlite-wasm:
- Library-agnostic public API (references "PostgreSQL WASM", not "PGlite")
- ~3MB bundle size documented for informed choice vs SQLite WASM
- No Node.js support (browser-only driver)
- Lazy WASM module loading

Files created:
- src/index.ts - Main PgWasmDriver class
- src/environment.ts - Environment detection utilities
- src/wasm-loader.ts - PGlite WASM lazy loader
- src/knex-adapter.ts - Custom Knex client for PGlite
- test/index.test.ts - Comprehensive unit tests
- README.md - Complete documentation
- package.json, tsconfig.json - Package configuration

All builds and tests passing.

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/drivers/pg-wasm/README.md

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+{
+  "name": "@objectql/driver-pg-wasm",
+  "version": "4.2.0",
+  "description": "PostgreSQL WASM driver for ObjectQL - Browser-native PostgreSQL database with IndexedDB/OPFS persistence",
+  "keywords": [
+    "objectql",
+    "driver",
+    "postgresql",
+    "postgres",
+    "wasm",
+    "webassembly",
+    "browser",
+    "pglite",
+    "opfs",
+    "indexeddb",
+    "database",
+    "adapter"
+  ],
+  "license": "MIT",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "default": "./dist/index.js"
+    }
+  },
+  "scripts": {
+    "build": "tsc",
+    "test": "vitest run"
+  },
+  "dependencies": {
+    "@electric-sql/pglite": "^0.1.5",
+    "@objectql/driver-sql": "workspace:*",
+    "@objectql/types": "workspace:*",
+    "@objectstack/spec": "^1.1.0",
+    "knex": "^3.1.0",
+    "nanoid": "^3.3.11",
+    "zod": "^3.24.1"
+  },
+  "devDependencies": {
+    "@types/node": "^20.0.0",
+    "pg": "^8.11.3",
+    "typescript": "^5.0.0",
+    "vitest": "^1.0.0"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/objectstack-ai/objectql.git",
+    "directory": "packages/drivers/pg-wasm"
+  }
+}

packages/drivers/pg-wasm/package.json

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+/**
+ * ObjectQL
+ * Copyright (c) 2026-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import { ObjectQLError } from '@objectql/types';
+
+/**
+ * Environment detection utilities for browser PostgreSQL WASM support
+ */
+
+/**
+ * Check if WebAssembly is available
+ */
+export function checkWebAssembly(): void {
+    if (typeof globalThis.WebAssembly === 'undefined') {
+        throw new ObjectQLError({
+            code: 'ENVIRONMENT_ERROR',
+            message: 'WebAssembly is not supported in this environment. PostgreSQL WASM driver requires WebAssembly support.'
+        });
+    }
+}
+
+/**
+ * Check if IndexedDB is available
+ */
+export async function checkIndexedDB(): Promise<boolean> {
+    try {
+        if (typeof indexedDB === 'undefined') {
+            return false;
+        }
+        
+        // Try to open a test database
+        return new Promise((resolve) => {
+            const request = indexedDB.open('__opfs_test__', 1);
+            request.onsuccess = () => {
+                request.result.close();
+                indexedDB.deleteDatabase('__opfs_test__');
+                resolve(true);
+            };
+            request.onerror = () => resolve(false);
+        });
+    } catch {
+        return false;
+    }
+}
+
+/**
+ * Check if OPFS (Origin Private File System) is available
+ */
+export async function checkOPFS(): Promise<boolean> {
+    try {
+        if (typeof navigator === 'undefined' || !navigator.storage) {
+            return false;
+        }
+        
+        // Check if getDirectory method exists
+        if (typeof (navigator.storage as any).getDirectory !== 'function') {
+            return false;
+        }
+        
+        // Try to actually access it
+        const root = await (navigator.storage as any).getDirectory();
+        return !!root;
+    } catch {
+        return false;
+    }
+}
+
+/**
+ * Detect the best available storage backend
+ */
+export async function detectStorageBackend(): Promise<'idb' | 'opfs' | 'memory'> {
+    const hasOPFS = await checkOPFS();
+    if (hasOPFS) {
+        return 'opfs';
+    }
+    
+    const hasIDB = await checkIndexedDB();
+    if (hasIDB) {
+        return 'idb';
+    }
+    
+    return 'memory';
+}