Scope the trailing-whitespace and escaping-scan rules, name the totality gap

spec/flavour.md

@@ -38,11 +38,12 @@ normalizes to it through the round-trip.
   CommonMark autolink (absolute URI).
 - Paragraphs on one line — no soft wrapping; a soft line break in input becomes a single space.
 - Entity references in input decode to their characters; output backslash-escapes only where text
-  would otherwise parse as syntax: escape the leading delimiter of a construct that would
-  otherwise open, re-scan from there, and repeat — with the opener literal the closer parses as
-  text, so `*not emphasis*` is `\*not emphasis*`, one backslash.
-- Blocks separated by one blank line, no trailing whitespace, single trailing newline; a document
-  with no blocks is the empty string.
+  would otherwise parse as syntax, scanning the assembled line rather than each text node: escape
+  the leading delimiter of a construct that would otherwise open, re-scan from there, and repeat —
+  with the opener literal the closer parses as text, so `*not emphasis*` is `\*not emphasis*`, one
+  backslash.
+- Blocks separated by one blank line, no trailing whitespace outside a code block's content,
+  single trailing newline; a document with no blocks is the empty string.
 
 ## Directives