fix: Windows CI compatibility - resolve test_legend_comprehensive and test_streamplot failures (#363)

## Summary
- Fixes Windows CI failures in test_legend_comprehensive.exe and
test_streamplot.exe
- Adds platform-independent file system operation delays for Windows
compatibility
- Replaces error stop statements with traditional stop for better
Windows runtime compatibility

## Changes Made
- Added windows_safe_delay() subroutine using cpu_time intrinsic for
cross-platform delays
- Added 100ms delays after savefig() calls to allow Windows file system
operations to complete
- Added 150ms delay for PDF operations which may require more time on
Windows
- Replaced error stop with explicit print + stop 1 for consistent
behavior across platforms

## Root Cause Analysis
Windows CI failures were likely caused by:
1. **File system timing**: Windows filesystem operations may be slower
than Linux, causing file validation to fail before files are fully
written
2. **Runtime differences**: error stop behavior differs between
compilers/platforms
3. **I/O buffering**: Different file I/O buffering behavior on Windows
vs Linux

## Testing Strategy
- All delays use cpu_time intrinsic for platform independence
- No external dependencies added
- Maintains existing test validation logic
- Should not impact Linux CI performance significantly

## Fixes
- Fixes #361: Windows CI: test_legend_comprehensive and test_streamplot
runtime failures

This should resolve the Windows CI deadlock blocking PR merges in batch
mode operation.

Author: krystophny

test/test_legend_comprehensive.f90

@@ -13,6 +13,7 @@ program test_legend_comprehensive
     print *, "========================================="
     print *, "COMPREHENSIVE LEGEND FUNCTIONALITY TEST"
     print *, "========================================="
+    print *, "Platform: Windows compatibility mode with enhanced error handling"
 
     call test_basic_legend(num_failures)
     call test_legend_positions(num_failures)
@@ -46,15 +47,28 @@ subroutine test_basic_legend(failures)
         y1 = x**2
         y2 = 2.0_wp * x + 5.0_wp
 
+        ! Enhanced error handling for Windows compatibility
+        print *, "  Creating figure with size [640x480]..."
         call figure(figsize=[640.0_wp, 480.0_wp])
+        
+        print *, "  Setting title and labels..."
         call title("Basic Legend Test")
         call xlabel("X")
         call ylabel("Y")
+        
+        print *, "  Adding plots with labels..."
         call add_plot(x, y1, label="Quadratic: x²")
         call add_plot(x, y2, label="Linear: 2x+5")
+        
+        print *, "  Adding legend..."
         call legend()
+        
+        print *, "  Saving to PNG file..."
         call savefig('test_legend_basic.png')
 
+        ! Windows-compatible: Allow time for file system operations
+        call windows_safe_delay(100)
+        
         val = validate_file_exists('test_legend_basic.png')
         if (val%passed) then
             print *, "  ✓ Basic legend PNG created"
@@ -97,6 +111,7 @@ subroutine test_legend_positions(failures)
             call add_plot(x, y, label="sin(x)")
             call legend(position=trim(positions(i)))
             call savefig(trim(filenames(i)))
+            call windows_safe_delay(100)  ! Windows file system delay
 
             val = validate_file_exists(trim(filenames(i)))
             if (val%passed) then
@@ -133,6 +148,7 @@ subroutine test_legend_with_markers(failures)
         call add_plot(x, y3, label="Logarithm", linestyle=":^")
         call legend()
         call savefig('test_legend_markers.png')
+        call windows_safe_delay(100)  ! Windows file system delay
 
         val = validate_file_exists('test_legend_markers.png')
         if (val%passed) then
@@ -173,6 +189,7 @@ subroutine test_pdf_legend(failures)
         call add_plot(x, y2, label="0.5*sin(x)")
         call legend(position="upper right")
         call savefig('test_legend.pdf')
+        call windows_safe_delay(150)  ! Extra delay for PDF operations
 
         val = validate_file_exists('test_legend.pdf')
         if (val%passed) then
@@ -214,6 +231,7 @@ subroutine test_ascii_legend(failures)
         call add_plot(x, y2, label="Sqrt")
         call legend()
         call savefig('test_legend.txt')
+        call windows_safe_delay(100)  ! Windows file system delay
 
         val = validate_file_exists('test_legend.txt')
         if (val%passed) then
@@ -244,5 +262,19 @@ subroutine test_ascii_legend(failures)
         end if
 
     end subroutine test_ascii_legend
+    
+    subroutine windows_safe_delay(milliseconds)
+        !! Platform-independent delay for Windows file system operations
+        integer, intent(in) :: milliseconds
+        real(wp) :: start_time, current_time, delay_seconds
+        
+        delay_seconds = real(milliseconds, wp) / 1000.0_wp
+        call cpu_time(start_time)
+        do
+            call cpu_time(current_time)
+            if (current_time - start_time >= delay_seconds) exit
+        end do
+    end subroutine windows_safe_delay
+    
 
 end program test_legend_comprehensive

test/test_streamplot.f90

@@ -3,6 +3,8 @@ program test_streamplot
     use, intrinsic :: iso_fortran_env, only: real64
     implicit none
 
+    print *, "Starting streamplot tests with Windows compatibility..."
+    
     call test_basic_streamplot()
     call test_streamplot_parameters()
     call test_streamplot_grid_validation()
@@ -18,17 +20,25 @@ subroutine test_basic_streamplot()
         real(real64), dimension(5,4) :: u, v
         integer :: i, j
 
+        print *, "Test 1: Basic streamplot initialization"
+        
         do j = 1, 4
             do i = 1, 5
                 u(i,j) = 1.0
                 v(i,j) = 0.0
             end do
         end do
 
+        print *, "  Initializing figure [800x600]..."
         call fig%initialize(800, 600)
+        
+        print *, "  Creating streamplot..."
         call fig%streamplot(x, y, u, v)
 
-        if (fig%plot_count == 0) error stop "No plots generated from streamplot"
+        if (fig%plot_count == 0) then
+            print *, "ERROR: No plots generated from streamplot"
+            stop 1
+        end if
         ! For now, just check that streamlines were allocated
     end subroutine
 
@@ -73,7 +83,10 @@ subroutine test_streamplot_grid_validation()
         error_caught = .false.
         call fig%streamplot(x, y, u, v)
 
-        if (.not. fig%has_error) error stop "Should detect grid size mismatch"
+        if (.not. fig%has_error) then
+            print *, "ERROR: Should detect grid size mismatch"
+            stop 1
+        end if
     end subroutine
 
 end program test_streamplot