Salvages PR #3976 by ksj5131513-ops, ported fresh onto current master and
re-applied on top of #4195's external-refresh gate (the original PR predated
#3916/#4195's rework of refreshActiveSessionIfExternallyUpdated).
Two parts:
1. Avoid an unconditional same-session force reload the moment streaming
settles. _scheduleActiveSessionIdleReload previously called
loadSession(force:true) on every idle reconcile, which on mobile PWA caused
a visible end-of-turn flash and could briefly restore the pane with stale
layout geometry. It now reconciles against server metadata first via
refreshActiveSessionIfExternallyUpdated('idle-reconcile', {ignoreStreamJustFinished:true})
— reloading ONLY when the message count actually changed — and falls back to
the original forced reload only if the metadata probe itself fails.
This COEXISTS with #4195: the poll-only external-session early-return
(if((reason||'poll')==='poll' && !_isExternalSession(S.session)) return) is
left untouched. The idle path uses a non-'poll' reason so it never trips that
gate, and opts (read via arguments[1], same pattern as loadSession) only
bypasses the post-stream cooldown, not the external gate. The function keeps
its (reason) signature and now returns a status string
('skipped'/'unchanged'/'reloaded'/'failed') for callers that want it.
2. Mobile viewport reflow guard for PWA visualViewport changes. When the
on-screen keyboard / browser chrome shows or hides, the phone layout can stay
painted against stale geometry. _forceMobileViewportReflow() toggles a
one-frame html.viewport-reflow class (cheap GPU-promotion transform) to force
a repaint, then resyncs the workspace panel + sidebar aria. Wired to
visualViewport resize/scroll (debounced) where available, falling back to the
window resize handler otherwise. Adds safe-area-inset padding to topbar,
messages-inner, and composer-wrap on phones. Uses overflow-x:clip (NOT hidden)
on .layout per the #4856 lesson to avoid coercing overflow-y into a scroller.
Co-authored-by: ksj5131513-ops <ksj5131513-ops@users.noreply.github.com>
