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/gal-regression/wasm/legacy_gl_stubs.js

@@ -0,0 +1,91 @@
+/**
+ * Legacy GL stubs for wxWidgets compatibility
+ *
+ * wxWidgets GL library may reference these functions at runtime even though:
+ * 1. wxGLAPI methods are stubbed as no-ops in C++ for WASM builds
+ * 2. KiCad doesn't use wxGLAPI - it has its own GAL
+ * 3. Our WEBGL_GAL uses modern WebGL 2.0 / OpenGL ES 3.0 only
+ *
+ * These no-op stubs satisfy the linker and runtime without affecting rendering.
+ * All actual rendering goes through WEBGL_GAL which uses VBOs and shaders.
+ */
+
+addToLibrary({
+  // Immediate mode rendering (replaced by VBOs in WEBGL_GAL)
+  glBegin: function(mode) {},
+  glEnd: function() {},
+
+  // Vertex submission (replaced by vertex manager in WEBGL_GAL)
+  glVertex2f: function(x, y) {},
+  glVertex3f: function(x, y, z) {},
+  glVertex2d: function(x, y) {},
+  glVertex3d: function(x, y, z) {},
+  glVertex4f: function(x, y, z, w) {},
+  glVertex4d: function(x, y, z, w) {},
+
+  // Color (replaced by vertex attributes/uniforms in WEBGL_GAL)
+  glColor3f: function(r, g, b) {},
+  glColor4f: function(r, g, b, a) {},
+  glColor3d: function(r, g, b) {},
+  glColor4d: function(r, g, b, a) {},
+  glColor3ub: function(r, g, b) {},
+  glColor4ub: function(r, g, b, a) {},
+
+  // Texture coordinates (replaced by vertex attributes in WEBGL_GAL)
+  glTexCoord2f: function(s, t) {},
+  glTexCoord2d: function(s, t) {},
+
+  // Normals (replaced by vertex attributes in WEBGL_GAL)
+  glNormal3f: function(nx, ny, nz) {},
+  glNormal3d: function(nx, ny, nz) {},
+
+  // Matrix mode (replaced by MVP matrix uniform in WEBGL_GAL)
+  glMatrixMode: function(mode) {},
+  glLoadIdentity: function() {},
+  glPushMatrix: function() {},
+  glPopMatrix: function() {},
+
+  // Projection (replaced by computeOrthoMatrix in WEBGL_GAL)
+  glOrtho: function(left, right, bottom, top, near, far) {},
+  glFrustum: function(left, right, bottom, top, near, far) {},
+
+  // Matrix operations (replaced by glm in WEBGL_GAL)
+  glLoadMatrixf: function(m) {},
+  glLoadMatrixd: function(m) {},
+  glMultMatrixf: function(m) {},
+  glMultMatrixd: function(m) {},
+  glTranslatef: function(x, y, z) {},
+  glTranslated: function(x, y, z) {},
+  glRotatef: function(angle, x, y, z) {},
+  glRotated: function(angle, x, y, z) {},
+  glScalef: function(x, y, z) {},
+  glScaled: function(x, y, z) {},
+
+  // Fixed function pipeline (not available in WebGL)
+  glShadeModel: function(mode) {},
+  glLightfv: function(light, pname, params) {},
+  glLightf: function(light, pname, param) {},
+  glMaterialfv: function(face, pname, params) {},
+  glMaterialf: function(face, pname, param) {},
+  glColorMaterial: function(face, mode) {},
+
+  // Legacy client state (replaced by glVertexAttribPointer in WEBGL_GAL)
+  glEnableClientState: function(array) {},
+  glDisableClientState: function(array) {},
+  glVertexPointer: function(size, type, stride, pointer) {},
+  glColorPointer: function(size, type, stride, pointer) {},
+  glTexCoordPointer: function(size, type, stride, pointer) {},
+  glNormalPointer: function(type, stride, pointer) {},
+
+  // Legacy texture environment (replaced by shaders in WEBGL_GAL)
+  glTexEnvf: function(target, pname, param) {},
+  glTexEnvi: function(target, pname, param) {},
+  glTexEnvfv: function(target, pname, params) {},
+
+  // glDrawBuffer (replaced by glDrawBuffers in WebGL 2.0)
+  glDrawBuffer: function(buf) {},
+
+  // Legacy index mode (not supported in WebGL)
+  glIndexi: function(c) {},
+  glIndexf: function(c) {},
+});