feat(webgl): Fix WebGL GAL rendering with proper coordinate setup

- Fix coordinate system for 1:1 pixel mapping (was using nm scale)
- Set worldUnitLength to 1/96 to match native test setup
- Add SetLookAtPoint and SetZoomFactor for proper view transformation
- Fix glDrawBuffers for WebGL 2.0 (array index must match attachment)
- Add legacy_gl_stubs.js for wxWidgets compatibility
- Add isReady() check to prevent race condition in Playwright tests

All 28 GAL test scenarios now render correctly in WebGL.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/e2e/gal-webgl.spec.ts

@@ -94,7 +94,7 @@ test.describe('GAL WebGL Regression Tests', () => {
 
       // Wait for module to be ready
       await page.waitForFunction(() => {
-        return (window as any).galTest !== undefined;
+        return (window as any).galTest !== undefined && (window as any).galTest.isReady();
       }, { timeout: 60000 });
 
       // Run the scenario