WIP docs: Proto log_help

Define `PrettyHelp` class with methods for declaring different parts of help message.
Currently able to produce standard help messages as expected.
Updates chformal to use (only) the new help_v2.
Currently makes use of a global static to track the current help context, allowing register.h to live in blissful ignorance and instead rely on help_v2 implementations calling `auto *help = PrettyHelp::get_current();` and `return true;` to minimise impact on rebuilds (i.e. not requiring every source file to be recompiled).

kernel/log_help.h

@@ -0,0 +1,51 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2025  Krystine Dawn <krystinedawn@yosyshq.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#ifndef LOG_HELP_H
+#define LOG_HELP_H
+
+#include "kernel/yosys_common.h"
+#include "kernel/json.h"
+
+YOSYS_NAMESPACE_BEGIN
+
+class PrettyHelp
+{
+	PrettyHelp *prior = nullptr;
+	int current_indent = 0;
+public:
+	PrettyHelp();
+	~PrettyHelp();
+
+	static PrettyHelp *get_current();
+
+	bool has_content();
+
+	void usage(const string &usage);
+	void option(const string &option, const string &description = "");
+	void codeblock(const string &code, const string &language = "none");
+	void paragraph(const string &text);
+
+	void optiongroup(const string &group = "");
+	void endgroup();
+};
+
+YOSYS_NAMESPACE_END
+
+#endif