* fix(ui): mount only the active session chat iframe
* repro(ui): mount-all-persisted session-chat iframes (#2815)
Adds a regression-style reproduction for issue #2815: ContextPanel
renders one full-application iframe for every chat tab (inactive tabs
are only hidden via the Tailwind 'hidden' class, never unmounted), so a
reload restores all persisted session-chat tabs from the ui-store and
mounts N embedded OpenChamber apps in one browser tab.
The test reads the real ContextPanel.tsx render block, drives the real
useUIStore with the issue's persisted scenario (11 tabs, 8 read-only
session-chat tabs), and models the render block with the real
buildEmbeddedSessionChatURL helper, showing 8 live src iframes (7
hidden but loaded).
* test(ui): adapt issue 2815 reproduction for active chat
* fix(ui): unmount session chat when panel closes
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Co-authored-by: ChangeHow <23733347+ChangeHow@users.noreply.github.com>
