fix: skip heading rendering when folded to same visual line

When org folds headings (S-TAB overview mode), the newline after
each heading becomes invisible, causing multiple headings to appear
on the same visual line.  posn-at-point then reports col > 1 for
headings that follow the fold ellipsis of a previous heading.

Placing scaled text at col > 1 causes horizontal drift — headings
rendered mid-line overlapping with fold ellipsis and each other.

Fix: org headings always start at buffer column 0.  If the computed
terminal column is not 1, the heading is in a folded context where
rendering at scale would be wrong.  Skip it (treat as not visible),
erase any previous placement, and let the refresh cycle re-place
it when unfolded.

Root cause identified via debug log analysis showing:
  Before fold: all headings at col=1 (correct)
  After S-TAB: headings at col=21/24 on same row (wrong)

0 files changed, 0 insertions, 0 deletions