Change Process::Status#to_s to hex format on Windows (#15285)

Status numbers on Windows are usually represented in hexadecimal notation. This applies that for all large exit status values (above `UInt16::MAX`, inspired from https://cs.opensource.google/go/go/+/refs/tags/go1.23.4:src/os/exec_posix.go;l=117-121).

This again improves usability because it's easier to interpret unknown status values and compare them with listings sharing the typical number format.

In #15283 we already changed `Status#to_s` to print the name of known values. But not all status codes are named.

spec/std/process/status_spec.cr

@@ -273,6 +273,14 @@ describe Process::Status do
         assert_prints Process::Status.new(Signal.new(126).value).to_s, "Signal[126]"
       end
     {% end %}
+
+    {% if flag?(:win32) %}
+      it "hex format" do
+        assert_prints Process::Status.new(UInt16::MAX).to_s, "0x0000FFFF"
+        assert_prints Process::Status.new(0x01234567).to_s, "0x01234567"
+        assert_prints Process::Status.new(UInt32::MAX).to_s, "0xFFFFFFFF"
+      end
+    {% end %}
   end
 
   describe "#inspect" do
@@ -302,5 +310,13 @@ describe Process::Status do
         assert_prints Process::Status.new(unknown_signal.value).inspect, "Process::Status[Signal[126]]"
       end
     {% end %}
+
+    {% if flag?(:win32) %}
+      it "hex format" do
+        assert_prints Process::Status.new(UInt16::MAX).inspect, "Process::Status[0x0000FFFF]"
+        assert_prints Process::Status.new(0x01234567).inspect, "Process::Status[0x01234567]"
+        assert_prints Process::Status.new(UInt32::MAX).inspect, "Process::Status[0xFFFFFFFF]"
+      end
+    {% end %}
   end
 end

src/process/status.cr

@@ -294,7 +294,7 @@ class Process::Status
       if name = name_for_win32_exit_status
         io << "LibC::" << name
       else
-        @exit_status.to_s(io)
+        stringify_exit_status_windows(io)
       end
     {% else %}
       if signal = exit_signal?
@@ -336,7 +336,7 @@ class Process::Status
       if name = name_for_win32_exit_status
         io << name
       else
-        @exit_status.to_s(io)
+        stringify_exit_status_windows(io)
       end
     {% else %}
       if signal = exit_signal?
@@ -358,7 +358,7 @@ class Process::Status
   # A signal exit status prints the name of the `Signal` member (`HUP`, `INT`, etc.).
   def to_s : String
     {% if flag?(:win32) %}
-      name_for_win32_exit_status || @exit_status.to_s
+      name_for_win32_exit_status || String.build { |io| stringify_exit_status_windows(io) }
     {% else %}
       if signal = exit_signal?
         signal.member_name || signal.inspect
@@ -367,4 +367,14 @@ class Process::Status
       end
     {% end %}
   end
+
+  private def stringify_exit_status_windows(io)
+    # On Windows large status codes are typically expressed in hexadecimal
+    if @exit_status >= UInt16::MAX
+      io << "0x"
+      @exit_status.to_s(base: 16, upcase: true).rjust(io, 8, '0')
+    else
+      @exit_status.to_s(io)
+    end
+  end
 end