feat: detect Scoop install on Windows for auto-upgrade #541

func gentleAIHint(profile system.PlatformProfile) string {
    switch profile.OS {
    case "windows":
        return "irm https://...install.ps1 | iex"  // Always irm, no Scoop detection
    }
}

func gentleAIHint(profile system.PlatformProfile) string {
    switch profile.OS {
    case "windows":
        if isScoopInstall() {
            return "scoop update gentle-ai"
        }
        return "irm https://...install.ps1 | iex"
    }
}

func isScoopInstall() bool {
    exe, err := os.Executable()
    if err != nil {
        return false
    }
    resolved, err := filepath.EvalSymlinks(exe)
    if err != nil {
        return false
    }
    return strings.Contains(strings.ToLower(resolved), filepath.Join("scoop", "apps", "gentle-ai"))
}

func binaryUpgrade(ctx context.Context, r update.UpdateResult, profile system.PlatformProfile) error {
    if profile.OS == "windows" {
        return &ManualFallbackError{
            Hint: fmt.Sprintf("upgrade %q on Windows requires manual update: %s", r.Tool.Name, hint),
        }
    }
}

func binaryUpgrade(ctx context.Context, r update.UpdateResult, profile system.PlatformProfile) error {
    if r.Tool.Name == "engram" {
        return engramBinaryUpgrade(profile)
    }
    if profile.OS == "windows" {
        if isScoopInstall() {
            return scoopUpgrade(ctx, r.Tool.Name)
        }
        return &ManualFallbackError{...}
    }
    return downloadAndReplace(ctx, r, profile)
}

func scoopUpgrade(ctx context.Context, toolName string) error {
    cmd := execCommand("scoop", "update", toolName)
    cmd.Stdin = nil
    if out, err := cmd.CombinedOutput(); err != nil {
        return fmt.Errorf("scoop update %s: %w (output: %s)", toolName, err, string(out))
    }
    return nil
}

const (
    InstallBrew      InstallMethod = "brew"
    InstallScoop     InstallMethod = "scoop"  // NEW
    InstallBinary    InstallMethod = "binary"
    // ...
)