The SSH renderer previously declared 'provisionalPendingPreview: "collapsed"',
which only opted the COLLAPSED pending shape out of the transcript's
stable-prefix ratchet. Once the user expanded an in-flight SSH preview (ctrl+o)
and the framed block outgrew the viewport, the pending rows became
ratchet-eligible and committed to native scrollback before the result render
inserted the 'Output' section. The settled render then re-anchored the frame,
producing two distinct stranded shapes in history:
- a stale 'pending SSH: [host]' header pinned above the final '<- SSH: [host]'
frame (header variant), and
- the pending bottom border row reused in-place as the new 'Output' separator,
with a fresh '...' footer pushed below it (footer variant).
Flip 'provisionalPendingPreview' to 'true' so every pending shape — collapsed
or expanded — is treated as provisional and stays out of native scrollback
until the result render commits a settled frame. The 'collapsed'-only opt-out
remains correct for renderers (bash, eval) whose expanded pending preview is
top-anchored and survives the result render without re-anchoring.
Added two contract tests asserting expanded pending SSH is commit-unstable
and that bash/eval expanded pending preview is still commit-stable — keeping
the opt-in renderer-scoped.
Fixes#3714
roboomp
2024821d67