feat(clipboard): add win32yank fallback for WSL2

y, p, paste, and hist now try win32yank.exe after wl-copy/wl-paste
and xclip, so clipboard access works under WSL2 once win32yank is
installed and reachable through WSL interop. Updates the OS
compatibility docs accordingly.

functions/hist.fish

@@ -12,7 +12,8 @@
 #
 # DESCRIPTION
 #   Searches fish history interactively using fzf, inserts the selected command
-#   into the command line, and copies it to the clipboard via wl-copy.
+#   into the command line, and copies it to the clipboard via wl-copy (falls
+#   back to win32yank on WSL2).
 #
 # EXIT STATUS
 #   0  Command selected and inserted, or fzf was cancelled
@@ -36,7 +37,11 @@ function hist --description 'Search fish history and put it in the prompt'
         # Strip the timestamp for the final output
         set -l command (echo $selected | string replace -r '^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2} ' '')
 
-        echo $command | wl-copy 2>/dev/null
+        if type -q wl-copy
+            echo $command | wl-copy 2>/dev/null
+        else if type -q win32yank.exe
+            echo $command | win32yank.exe -i --crlf 2>/dev/null
+        end
         commandline -r $command
     end
 end