The structural prose parser — a [Parser] adapter.
A logos lexer turns text into mechanical tokens (words, numbers, sentence
terminators, quotes, punctuation), and a small segmenter groups them into
[Node::Sentence] runs (absorbing a trailing closing quote or bracket). It
produces structure only — it makes no part-of-speech decisions; that is the
lexicon and annotator's job. (This is sentence segmentation, not a deep
recursive-descent grammar; the structure is intentionally shallow in v0.)
Parsing is total: any input, including malformed or non-ASCII text,
yields a [Tree] without panicking. Characters the lexer cannot otherwise
classify are emitted as punctuation rather than dropped.