Say why blocks() is handed sizes it could reach for

Every field of HelpSizes is on the ParseResult too, so this reads like
the parameter usageText() just lost. It is not one. A text width of zero
means ask, sizes carries the answer rather than the zero, and the answer
is settled once and handed to render() as well. An override working it
out again would call console::width() a second time, and a terminal
resized between the two halves would lay the usage line out to one width
and the descriptions to another.

The cpp said this beside the code that does it. The header, which is
where somebody asks the question, did not.

Author: SineStriker

include/stdcorelib/support/commandline.h

@@ -1562,6 +1562,11 @@ namespace stdc::cli {
 
         /// What the help text is made of, in the order ParseResult::helpLayout() asks for and
         /// with the groups a CommandCatalogue asks for already split.
+        ///
+        /// \note \a sizes is not what \a result was given, and is not to be worked out again
+        ///       from it. A text width of zero means ask, and this is the answer, settled once
+        ///       and handed to render() as well, so that a terminal resized in between cannot
+        ///       lay the usage line out to one width and the descriptions to another.
         virtual std::vector<HelpBlock> blocks(const ParseResult &result,
                                               const HelpSizes &sizes) const;