shell-integration: append $GHOSTTY_BIN_DIR to $PATH

For consistency with the termio/Exec.zig implementation, we always
append to the PATH (lowest priority).

src/shell-integration/elvish/lib/ghostty-integration.elv

@@ -198,7 +198,7 @@
   }
   if (and (has-value $features path) (has-env GHOSTTY_BIN_DIR)) {
     if (not (has-value $paths $E:GHOSTTY_BIN_DIR)) {
-        set paths = [$E:GHOSTTY_BIN_DIR $@paths]
+        set paths = [$@paths $E:GHOSTTY_BIN_DIR]
     }
   }
   if (and (has-value $features sudo) (not-eq "" $E:TERMINFO) (has-external sudo)) {

src/shell-integration/fish/vendor_conf.d/ghostty-shell-integration.fish

@@ -63,7 +63,7 @@ function __ghostty_setup --on-event fish_prompt -d "Setup ghostty integration"
 
     # Add Ghostty binary to PATH if the path feature is enabled
     if contains path $features; and test -n "$GHOSTTY_BIN_DIR"
-        fish_add_path "$GHOSTTY_BIN_DIR"
+        fish_add_path --append "$GHOSTTY_BIN_DIR"
     end
 
     # When using sudo shell integration feature, ensure $TERMINFO is set