Covers the flyout lifecycle (footer button, toggle, header-back
visibility tracking thread/list view), the pick-view detour, DOM
structural invariants (peer strip inside thread view, form/input/send
present) and the three read-only chat endpoints. Send/receive requires
a real relay and is intentionally skipped.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
