feat: add C++ support with ImGui/ImPlot framework and vendor submodules

Añade soporte C++ al registry: vendor submodules (glfw, imgui, implot, tracy),
sistema de build con CMake y toolchains cross-platform, runner C++ en fn CLI,
parser de tests Google Test, y funciones bash para build Linux/Windows.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/fn/cpprunner.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"fn-registry/registry"
+)
+
+func buildCppCommand(fn *registry.Function, registryRoot, absPath string, args []string) (*exec.Cmd, error) {
+	cppRoot := filepath.Join(registryRoot, "cpp")
+	buildDir := filepath.Join(cppRoot, "build", "linux")
+
+	// Ensure build directory exists and cmake is configured
+	if _, err := os.Stat(filepath.Join(buildDir, "CMakeCache.txt")); os.IsNotExist(err) {
+		fmt.Fprintf(os.Stderr, "[fn run] configuring cmake for cpp...\n")
+		configure := exec.Command("cmake", "-B", buildDir, "-S", cppRoot)
+		configure.Dir = registryRoot
+		configure.Stdout = os.Stderr
+		configure.Stderr = os.Stderr
+		if err := configure.Run(); err != nil {
+			return nil, fmt.Errorf("cmake configure failed: %w", err)
+		}
+	}
+
+	dir := filepath.Dir(absPath)
+
+	// Check if the function's directory has its own CMakeLists.txt (app with main)
+	localCMake := filepath.Join(dir, "CMakeLists.txt")
+	hasMain := false
+	if _, err := os.Stat(localCMake); err == nil {
+		hasMain = true
+	}
+	// Also check for main.cpp in the same directory
+	mainCpp := filepath.Join(dir, "main.cpp")
+	if _, err := os.Stat(mainCpp); err == nil {
+		hasMain = true
+	}
+
+	if hasMain {
+		// Build and run the app binary
+		targetName := filepath.Base(dir)
+		build := exec.Command("cmake", "--build", buildDir, "--target", targetName)
+		build.Dir = registryRoot
+		build.Stdout = os.Stderr
+		build.Stderr = os.Stderr
+		fmt.Fprintf(os.Stderr, "[fn run] building target %s...\n", targetName)
+		if err := build.Run(); err != nil {
+			return nil, fmt.Errorf("cmake build failed: %w", err)
+		}
+
+		// Find the built binary
+		binaryPath := findBinary(buildDir, targetName)
+		if binaryPath == "" {
+			return nil, fmt.Errorf("built binary %q not found in %s", targetName, buildDir)
+		}
+
+		cmd := exec.Command(binaryPath, args...)
+		cmd.Dir = dir
+		return cmd, nil
+	}
+
+	// Library code: compile-check only (like go vet)
+	build := exec.Command("cmake", "--build", buildDir)
+	build.Dir = registryRoot
+	build.Stdout = os.Stderr
+	build.Stderr = os.Stderr
+	fmt.Fprintf(os.Stderr, "[fn run] %s is library code — running compile check\n", fn.ID)
+
+	if err := build.Run(); err != nil {
+		return nil, fmt.Errorf("compile check failed: %w", err)
+	}
+
+	// Return a no-op command that just prints success
+	cmd := exec.Command("echo", fmt.Sprintf("[fn run] %s compiled successfully", fn.ID))
+	return cmd, nil
+}
+
+// findBinary searches for an executable in the build tree.
+func findBinary(buildDir, name string) string {
+	// Common locations cmake puts binaries
+	candidates := []string{
+		filepath.Join(buildDir, name),
+		filepath.Join(buildDir, "apps", name, name),
+	}
+
+	for _, c := range candidates {
+		if info, err := os.Stat(c); err == nil && !info.IsDir() {
+			// Check if executable
+			if info.Mode()&0111 != 0 {
+				return c
+			}
+		}
+	}
+
+	// Walk the build directory as fallback
+	var found string
+	filepath.Walk(buildDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil || info.IsDir() {
+			return nil
+		}
+		if info.Name() == name && info.Mode()&0111 != 0 {
+			found = path
+			return filepath.SkipAll
+		}
+		return nil
+	})
+
+	// Also try without extension match for paths with subdirectories
+	if found == "" {
+		filepath.Walk(buildDir, func(path string, info os.FileInfo, err error) error {
+			if err != nil || info.IsDir() {
+				return nil
+			}
+			base := strings.TrimSuffix(info.Name(), filepath.Ext(info.Name()))
+			if base == name && info.Mode()&0111 != 0 {
+				found = path
+				return filepath.SkipAll
+			}
+			return nil
+		})
+	}
+
+	return found
+}

cmd/fn/run.go

@@ -103,6 +103,8 @@ func buildCommand(fn *registry.Function, db *registry.DB, registryRoot, absPath
 		return buildBashCommand(absPath, args)
 	case "ts":
 		return buildTsCommand(registryRoot, absPath, args)
+	case "cpp":
+		return buildCppCommand(fn, registryRoot, absPath, args)
 	default:
 		return nil, fmt.Errorf("unsupported lang %q for execution", fn.Lang)
 	}