docscheck: tier-3 span walk stops at a wrapped signature's ) line

open   by a73x

tools/docscheck.zig ~570-581 measures a doc block against a span that ends on the first line matching the closing paren of a multi-line signature, so a wrapped pub fn is worth ~99 bytes of budget and a one-line 124-char signature passes. Three dedup fix rounds were shaped by this (fromSpec's signature, showsSelf's headroom). Fix the walk, then re-wrap. Found 2026-08-29.