Whole-line matching broke on any content long enough to wrap, so compare
against a whitespace-collapsed blob instead and check leftover header
markers separately against the rendered lines. Verified against headers
and body lines that wrap over 2-3 lines.
Add an append regression: append_file re-renders the whole document, so
put the markup that trips ReportLab in the appended half to exercise
that path on its own. Both PDF tests fail without the escape fix.
Also condense the stale three-line comment above the render loop.
Saurav Panda
e6b92bec56