Derive app keyboard offsets from one provider-owned shared value so chat content, composer surfaces, and floating panels share the same policy.
Treat progress-zero keyboard samples as closed, even if Android reports a stale nonzero height.
Position portal content relative to its render host so the composer anchor stays correct when surrounding layout shifts. This preserves the Portal surface needed for Android scrolling and touch behavior.
The popover was positioned `bottom: 100%` of its parent inside the composer
and worked on iOS/web; Android's hit-test by parent bounds drops touches on
children that overflow their parent, so taps and scrolls went through to the
chat behind it. Move the popover into a `<Portal>` at the app root and apply
the same Reanimated keyboard SharedValue as the composer so it tracks the
keyboard in lockstep. New `docs/floating-panels.md` captures the gotchas
(Android hit-test, Portal lifecycle/transforms, status-bar offset, the
two-measurement flash) and the canonical files.
