Prefer Peggy as the canonical single source for Publish parsing

Prefer Peggy as the canonical single source for Publish title parsing and format documentation. Chose one grammar with generated parser and synchronized documentation over regexes, inline parsers, or manually duplicated docs because format drift creates incompatible accepted inputs. Generate the parser reproducibly with a checked-in generator and stale-generation check; generate or synchronize docs/publish-issue-format.md from the grammar. Keep complex workflow JavaScript in runnable Node modules where practical.