fix: Windows CI compatibility - add file system delays and error handling

- Add windows_safe_delay() for file system operations in legend tests
- Replace error stop with traditional stop statements for Windows compatibility
- Add extra delay for PDF operations which may be slower on Windows
- Implement platform-independent delay using cpu_time intrinsic

Addresses failing Windows CI tests: test_legend_comprehensive.exe and test_streamplot.exe
Fixes #361

Author: krystophny

test/test_legend_comprehensive.f90

@@ -55,6 +55,9 @@ subroutine test_basic_legend(failures)
         call legend()
         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 +100,7 @@ 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 +137,7 @@ 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 +178,7 @@ 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 +220,7 @@ 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 +251,18 @@ 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

@@ -28,7 +28,10 @@ subroutine test_basic_streamplot()
         call fig%initialize(800, 600)
         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 +76,10 @@ 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