help: start grinding away at help text generation

I am resisting the urge to try to codegolf this into fewer lines. It's
going to end up being a sprawl, but it is what it is. The main part of
this that will actually require intelligent thought is the column
wrapping and alignment. I think I will probably be implementing a
custom writer style thing to handle that.

There are a lot of annoying loose odds and ends here. Choice types
should list all the choices. But we can't necessarily assume that an
enum-typed parameter is a choice type (only if it uses the default
converter). Perhaps the conversion stuff should be turned into an
interface that can also be responsible for converting the default
value and providing additional information. For now I will probably
just hack it so that I can move on to other things.

demo/demo.zig

@@ -16,12 +16,17 @@ const cli = cmd: {
         .short_tag = "-t",
         .long_tag = "--test",
         .env_var = "NOCLIP_TEST",
+        .description = "multi-value test option",
+        .nice_type_name = "int> <int",
     });
     cmd.add_option(.{ .OutputType = Choice }, .{
         .name = "choice",
         .short_tag = "-c",
         .long_tag = "--choice",
+        .default = .second,
         .env_var = "NOCLIP_CHOICE",
+        .description = "enum choice option",
+        .nice_type_name = "choice",
     });
     cmd.add_option(.{ .OutputType = u32 }, .{
         .name = "default",
@@ -29,23 +34,28 @@ const cli = cmd: {
         .long_tag = "--default",
         .env_var = "NOCLIP_DEFAULT",
         .default = 100,
+        .description = "default value integer option",
+        .nice_type_name = "uint",
     });
     cmd.add_option(.{ .OutputType = u8, .multi = true }, .{
         .name = "multi",
         .short_tag = "-m",
         .long_tag = "--multi",
         .env_var = "NOCLIP_MULTI",
+        .description = "multiple specification test option",
     });
     cmd.add_flag(.{}, .{
         .name = "flag",
         .truthy = .{ .short_tag = "-f", .long_tag = "--flag" },
-        .falsy = .{ .long_tag = "--no-flag" },
+        .falsy = .{ .short_tag = "-F", .long_tag = "--no-flag" },
         .env_var = "NOCLIP_FLAG",
+        .description = "boolean flag",
     });
     cmd.add_flag(.{ .multi = true }, .{
         .name = "multiflag",
         .truthy = .{ .short_tag = "-M" },
         .env_var = "NOCLIP_MULTIFLAG",
+        .description = "multiple specification test flag ",
     });
     cmd.add_argument(.{ .OutputType = []const u8 }, .{
         .name = "arg",