Bound the trailing legend entry at its source line, and parse hyphen-joined markers

Two independent corrector-logic defects, both hit by 6724771:

The trailing affiliation entry is bounded only by the end of the banner
region, so a poster whose abstract follows the legend with no header
between them let entry 7 swallow the whole abstract; the entry then
tripped the ran-into-body guard and the entire parse was discarded.
_banner_region now newline-joins its lines instead of flattening them to
spaces, so the trailing entry can fall back to the end of its own source
line. The fallback only runs when the entry would otherwise be thrown
away, and the line-bounded text must itself look like a clean
affiliation, so an affiliation that legitimately wraps is never
truncated. Entry text is whitespace-collapsed on the way out, keeping
the parsed strings identical to before.

_parse_marker_run rejected "4-5-6" outright: it matched neither the
two-endpoint range form nor a bare digit, so Hallin resolved to no
marker and the poster bailed. A hyphen chain of three or more numbers
cannot be a range, so it is now read as a joined marker list. Two-number
forms keep their range reading.

4560930 LOGIC-GAP to PASS and 6724771 LOGIC-GAP to ORDER-GAP (its
corrector logic is now correct on ideal order; its remaining failure is
reading order, where xy_cut merges the legend and abstract into one
block). Logic-OK now 11/13, AFFIL 9/13 end-to-end, 17/21 acceptable.
Zero per-poster metric change anywhere, suite green (260 passed).

Author: jimnoneill