Message history (DM + channel) now stacks bubbles upward from the compose
row instead of the header, so the newest message sits at the bottom like
a typical messenger, with older messages progressively above. UP/DOWN and
the scrollbar direction are swapped to match; the newest bubble now keeps
the same breathing-room gap against the compose row as it does against
another bubble, instead of touching it.
Keyboard: Shift is one-shot by default (capitalises just the next
letter, then reverts), with Hold-Enter on Shift toggling a persistent
caps-lock for the old sticky behavior. Hold-Enter on Backspace clears
the whole field in one action.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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