[QuadnucYard]

Value-level combinators implementing Pretty, so a document can be described without an allocator and materialized later through DocAllocator::pretty. Templates then compose as ordinary values (tuples, arrays, Option, iterators) instead of materializing each subexpression early.

• Nullary tokens (nil, fail, hard_line, line_or_nil, line_or_space, soft_line_or_nil, soft_line_or_space, space, spaces, expand_parent) are Copy; wrappers derive conditional Clone, so a token can be reused as an intersperse separator.
• Cover the layout, alternative and iteration operations: nest/indent/dedent (curried), group, align, dedent_to_root, flatten, line_suffix, union, partial_union, flat_alt, concat, intersperse, repeat; on_column and on_nesting under contextual.
• No text combinator: &str, String and Cow<str> already implement Pretty; as_string handles other Display values.
• Declarations generated by token_combinator!/unary_combinator!/ binary_combinator!; re-exported from prelude.