fix: auto-install python3-venv when ensurepip is missing on Linux

On Ubuntu/Debian, python3 is often pre-installed but python3-venv is
not, causing venv creation to fail with "ensurepip is not available".
Now detects this error and auto-installs the matching python3.x-venv
package via apt-get before retrying.

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

edge-ai-platform/installer/app.go

@@ -424,7 +424,24 @@ func (inst *Installer) setupPythonVenv(installDir string) error {
 
 	cmd := exec.Command(pythonPath, "-m", "venv", venvDir)
 	if out, err := cmd.CombinedOutput(); err != nil {
-		return fmt.Errorf("venv creation failed: %s — %w", string(out), err)
+		// On Linux, ensurepip may be missing — install python3-venv and retry
+		if runtime.GOOS == "linux" && strings.Contains(string(out), "ensurepip") {
+			inst.emitProgress(ProgressEvent{
+				Step:    "python",
+				Message: "Installing python3-venv package...",
+				Percent: 77,
+			})
+			if installErr := inst.installPython3Venv(pythonPath); installErr != nil {
+				return fmt.Errorf("venv creation failed and python3-venv install failed: %w", installErr)
+			}
+			// Retry venv creation
+			cmd = exec.Command(pythonPath, "-m", "venv", venvDir)
+			if out2, err2 := cmd.CombinedOutput(); err2 != nil {
+				return fmt.Errorf("venv creation still failed after installing python3-venv: %s — %w", string(out2), err2)
+			}
+		} else {
+			return fmt.Errorf("venv creation failed: %s — %w", string(out), err)
+		}
 	}
 
 	inst.emitProgress(ProgressEvent{

edge-ai-platform/installer/platform_darwin.go

@@ -73,6 +73,11 @@ func (inst *Installer) autoInstallPython3() error {
 	return nil
 }
 
+// installPython3Venv is a no-op on macOS (venv is bundled with Python).
+func (inst *Installer) installPython3Venv(pythonPath string) error {
+	return fmt.Errorf("python3-venv not available — please reinstall Python 3")
+}
+
 func installLibusb(installDir string) error {
 	if _, err := exec.LookPath("brew"); err != nil {
 		return fmt.Errorf("Homebrew not found. Install from https://brew.sh then retry")

edge-ai-platform/installer/platform_linux.go

@@ -136,6 +136,31 @@ func (inst *Installer) autoInstallPython3() error {
 	return nil
 }
 
+// installPython3Venv installs the python3-venv package matching the Python version.
+func (inst *Installer) installPython3Venv(pythonPath string) error {
+	if _, err := exec.LookPath("apt-get"); err != nil {
+		return fmt.Errorf("apt-get not found — please install python3-venv manually")
+	}
+
+	// Detect Python minor version to install the matching venv package
+	// e.g. python3.12 -> python3.12-venv
+	out, err := exec.Command(pythonPath, "-c", "import sys; print(f'{sys.version_info.major}.{sys.version_info.minor}')").Output()
+	if err != nil {
+		// Fallback to generic package
+		cmd := exec.Command("pkexec", "apt-get", "install", "-y", "python3-venv")
+		return cmd.Run()
+	}
+
+	ver := strings.TrimSpace(string(out))
+	pkg := fmt.Sprintf("python%s-venv", ver)
+
+	cmd := exec.Command("pkexec", "apt-get", "install", "-y", pkg)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("apt-get install %s failed: %s — %w", pkg, string(out), err)
+	}
+	return nil
+}
+
 func installFfmpeg(inst *Installer, needFfmpeg, needYtdlp bool) error {
 	if _, err := exec.LookPath("apt-get"); err != nil {
 		return fmt.Errorf("package manager not found — please install ffmpeg manually")

edge-ai-platform/installer/platform_windows.go

@@ -114,6 +114,11 @@ func (inst *Installer) autoInstallPython3() error {
 	return nil
 }
 
+// installPython3Venv is a no-op on Windows (venv is bundled with Python).
+func (inst *Installer) installPython3Venv(pythonPath string) error {
+	return fmt.Errorf("python3-venv not available — please reinstall Python 3")
+}
+
 func installLibusb(installDir string) error {
 	// 1. Extract libusb-1.0.dll from payload
 	dllDest := filepath.Join(installDir, "libusb-1.0.dll")