object_rework: working MVP with runtime CommandNode tree

- BaseCommandNode (abstract) / CommandNode(T) split for heterogeneous tree
- Flag(T) with compile-time type branching, Parsable/Coercable modules
- Arg double-process invariant enforcement
- App.generate macro builds CommandNode tree from Command subclasses
- Command#initialize generated via macro finished, populates ivars from handler
- Reserved -h/--help enforcement in Flag#check!
- MatchType::Help added, SubCommand dispatch fixed
- design.adoc: added Planned Features (markdown docs, bash completion)
- Makefile: tabs, .DEFAULT_GOAL, doc_show target

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/cligen/command/argument.cr

@@ -1,14 +1,21 @@
 module CliGen
   class Command
-    macro argument(variable, short, long, description, validation = nil)
+    macro argument(variable, long, description, short = nil, validation = nil, on_match = nil)
       {% raise "ERROR : CliGen::Command.argument : First argument (#{variable}) must be a TypeDeclaration (ex: '<var> : <type> [= val]')" unless variable.is_a? TypeDeclaration %}
-      {% name = variable.name %}
+      {% name = variable.var %}
       {% type = variable.type %}
-      {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided short must be a string" unless short.is_a? StringLiteral || string == nil %}
+      {% if short %}
+        {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided short must be a string" unless short.is_a? StringLiteral %}
+      {% end %}
       {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided long must be a string" unless long.is_a? StringLiteral || long == nil %}
       {% raise "ERROR : CliGen::Command.argument(#{name}) : You must provide a short or long" unless long || short %}
       {% raise "ERROR : CliGen::Command.argument(#{name}) : You must provide a description" unless description %}
       {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided description must be a String" unless description.is_a? StringLiteral %}
+      {% unless on_match.nil? %}
+        {% puts on_match %}
+        {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided on_match must be a Proc" unless on_match.is_a? ProcLiteral %}
+        {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided on_match return type must be a Bool" unless on_match.return_type == Nil %}
+      {% end %}
       {% unless validation.nil? %}
         {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided validation must be a Proc" unless validation.is_a? ProcLiteral %}
         {% raise "ERROR : CliGen::Command.argument(#{name}) : Provided validation return type must be a Bool" unless validation.return_type == Bool %}
@@ -23,7 +30,7 @@ module CliGen
       @[CliGen::Argument(short: {{short}}, long: {{long}}, description: {{description}}, validation: {{validation}}, on_match: {{on_match}})]
       @{{variable}}
 
-      def {{variable.name}}= (value : {{type}})
+      def {{variable.var}}= (value : {{type}})
         {% unless validation.nil? %}
           raise "ERROR : #{@type.name}##{@def.name} : Provided value #{value} is not passing validation" unless {{validation}}.call(value)
         {% end %}