Direct-chat composer no longer scrolls on focus (which aborted the iOS keyboard
raise on every tap after a dismiss). Layout-viewport drift is now undone on blur
— immediately plus a short follow-up cancelled on the next focus — so each focus
starts at scrollY 0 and the keyboard lock's scrollTo is a no-op.
Also hide the mobile bottom nav while the keyboard is up: it previously pinned to
bottom:0 and relied on the keyboard to cover it, but on iOS the layout viewport
does not shrink, so the bar overlapped the composer. It now slides off-screen
(translateY(100%) + pointer-events:none); safe because the nav is a sibling of
the input, not an ancestor.
Folds into the existing iOS chat-keyboard changeset.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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