fix: post navigation over ALL posts incl. pinned (no more pinned-only stack)
A pinned post showed only the pinned-stack navigation at the bottom. Now
Newer/Older runs through all posts in canonical feed order: solo = pinned
first by rank, then by date (same as the homepage); hub = globally by date.
Pinned posts simply sit in the continuous sequence. Neighbours determined
by index in that ordered list. The separate pinned-stack navigation
(PREVIOUS PINNED / TOP / BOTTOM) has been removed.
Co-Authored-By: Claude <noreply@…>
![(please configure the [header_logo] section in trac.ini)](/chrome/site/your_project_logo.png){kind=logo}
