fix: Correct GPU Go generator embed filename to use source file basename

Previously, the GPU Go generator used the package name for the
//go:embed directive (e.g., "main.wgsl"), but the WGSL file was
generated using the source filename (e.g., "calculator.wgsl").
This caused build failures when package name != source filename.

Changes:
- Updated GPUGoGenerator to accept shaderFilename parameter
- Modified cmd/guix/main.go to extract and pass basename.wgsl
- Updated all tests to pass shader filename to generator
- Verified with E2E tests and pre-commit checks

This ensures the embed directive always references the correct
WGSL file generated from the source .gx file.

Author: claude

cmd/guix/main.go

@@ -285,7 +285,10 @@ func generateFile(srcPath string, p *parser.Parser, verbose bool, verboseLogs bo
 		}
 
 		// Generate GPU Go structs
-		gpuGoGen := codegen.NewGPUGoGenerator(file.Package)
+		// Extract base filename for embed directive
+		baseName := filepath.Base(strings.TrimSuffix(srcPath, guixExt))
+		shaderFilename := baseName + ".wgsl"
+		gpuGoGen := codegen.NewGPUGoGenerator(file.Package, shaderFilename)
 		gpuGoOutput, err := gpuGoGen.Generate(file)
 		if err != nil {
 			return fmt.Errorf("failed to generate GPU Go code: %w", err)

pkg/codegen/e2e_wgsl_test.go

@@ -85,7 +85,7 @@ func fsMain(@location(0) color vec4) vec4 {
 	}
 
 	// Generate GPU Go code
-	gpuGoGen := NewGPUGoGenerator(file.Package)
+	gpuGoGen := NewGPUGoGenerator(file.Package, "shaders.wgsl")
 	gpuGoOutput, err := gpuGoGen.Generate(file)
 	if err != nil {
 		t.Fatalf("Failed to generate GPU Go code: %v", err)
@@ -187,7 +187,7 @@ func fsCandle(@location(0) color vec4) vec4 {
 	}
 
 	// Generate Go code
-	gpuGoGen := NewGPUGoGenerator(file.Package)
+	gpuGoGen := NewGPUGoGenerator(file.Package, "candle.wgsl")
 	gpuGoOutput, err := gpuGoGen.Generate(file)
 	if err != nil {
 		t.Fatalf("Failed to generate GPU Go code: %v", err)

pkg/codegen/gpu_go_generator.go

@@ -14,15 +14,17 @@ import (
 
 // GPUGoGenerator generates Go code from GPU struct declarations
 type GPUGoGenerator struct {
-	fset *token.FileSet
-	pkg  string
+	fset           *token.FileSet
+	pkg            string
+	shaderFilename string
 }
 
 // NewGPUGoGenerator creates a new GPU Go code generator
-func NewGPUGoGenerator(pkg string) *GPUGoGenerator {
+func NewGPUGoGenerator(pkg string, shaderFilename string) *GPUGoGenerator {
 	return &GPUGoGenerator{
-		fset: token.NewFileSet(),
-		pkg:  pkg,
+		fset:           token.NewFileSet(),
+		pkg:            pkg,
+		shaderFilename: shaderFilename,
 	}
 }
 
@@ -45,7 +47,7 @@ func (g *GPUGoGenerator) Generate(file *guixast.File) ([]byte, error) {
 
 	// Generate shader source constant
 	if len(file.GPUStructs) > 0 || len(file.GPUFunctions) > 0 {
-		embedDecl := g.generateShaderEmbed(file.Package)
+		embedDecl := g.generateShaderEmbed()
 		decls = append(decls, embedDecl...)
 	}
 
@@ -269,14 +271,14 @@ func (g *GPUGoGenerator) generateSizeCheckInit(gpuStruct *guixast.GPUStructDecl)
 }
 
 // Generate shader embed declarations
-func (g *GPUGoGenerator) generateShaderEmbed(pkgName string) []ast.Decl {
+func (g *GPUGoGenerator) generateShaderEmbed() []ast.Decl {
 	return []ast.Decl{
 		// Comment directive
 		&ast.GenDecl{
 			Tok: token.VAR,
 			Doc: &ast.CommentGroup{
 				List: []*ast.Comment{
-					{Text: fmt.Sprintf("//go:embed %s.wgsl", pkgName)},
+					{Text: fmt.Sprintf("//go:embed %s", g.shaderFilename)},
 				},
 			},
 			Specs: []ast.Spec{