chore(justfile): one-line install-man comment and long flag forms

Assisted-by: GLM 5.3

justfile

@@ -1,7 +1,8 @@
 # gasm-devkit.
 #
 # Replace gasm-devkit here and the values in the variable block. Everything below the block
-# is the standard set and is identical in every repository; see the `justfile` skill.
+# is the standard recipe set: the names and their meanings are fixed, identical in every
+# repository, and `gates` is the definition of done.
 binary := "gasm"
 package := "./cmd/gasm"
 
@@ -88,14 +89,13 @@ install: build
 uninstall:
     rm -f "{{bindir}}/{{binary}}"
 
-# Install the man pages under docs/man into mandir/man1, gzip-compressed. Not a gate: a
+# Install the man pages under docs/man into mandir/man1, gzip-compressed; not a gate.
-# convenience for the person at the keyboard; man finds them through ~/.local/share/man.
 install-man:
     #!/usr/bin/env perl
     my $out = $ENV{MANDIR} . q{/man1};
-    system(q{mkdir}, q{-p}, $out) == 0 or die qq{mkdir $out: $!\n};
+    system(q{mkdir}, q{--parents}, $out) == 0 or die qq{mkdir $out: $!\n};
     for my $p (glob q{docs/man/*.1}) {
-        open(my $g, q{-|}, q{gzip}, q{-c}, $p) or die qq{gzip $p: $!\n};
+        open(my $g, q{-|}, q{gzip}, q{--stdout}, $p) or die qq{gzip $p: $!\n};
         my $content = do { local $/; <$g> };
         close($g);
         my $base = $p;