Table row parsers are speculatively tried at every paragraph line
boundary via the terminator continuation. Each of the three row
variants would fully inline-parse the line before failing for lack of
a cell separator, so every paragraph line was inline-parsed several
times.
Since cell separators (whitespace followed by pipes) cannot span
lines, scanning the raw line for one lets us reject non-table lines
without any inline parsing. The check is conservative and never
rejects a line a row parser could accept.
Together with the previous commit, this makes the reader 4.3x faster
on a 1.6 MB test document and reduces heap allocation by 87%.
Co-Authored-By: Claude <noreply@anthropic.com>
