5b2: make the pipe escape terminate, cap the value a document fault echoes

AGENTS.md

@@ -91,9 +91,10 @@ Pre-1.0, normal 0.x rules.
 The error surface is a contract too. `ConvertError` is `{ code, message, path, position? }` — the
 code from a closed list a consumer may switch exhaustively, the message free text, the path the
 node's place from the document root, the position where a parse read the refusal in its input.
-A message reads `rule: violation` — a rule alone states a truth the reader must invert before it
-reads as a failure — and where the flavour's claim refuses ordinary prose it names the escape that
-unclaims the form claimed: `\:::` or `\|` for a line, `\:` for an inline directive.
+A message names the violation, not the rule alone — a rule by itself states a truth the reader
+must invert before it reads as a failure — and where the flavour's claim refuses ordinary prose it
+names the escape that unclaims the form claimed: `\:::` for a directive line, `\|` for every pipe
+row, `\:` for an inline directive.
 Adding, removing or renaming a code is breaking, so a milestone meeting a new failure cause
 reuses a code where one fits; the list is complete at `0.1.0`. A code names the
 cause; where one cause recurs across node types or across directions, one code covers them all and