The DM/room and channel history lists drew each message box's selection frame
and the bottom-left [+ send] button with byte-identical inline code. Extract
two small static helpers (drawHistRowFrame, drawComposeButton) and route both
lists through them.
Only the parts that were already identical are unified — the divergent
per-type logic (sender parsing, ACK semantics, body handling) stays inline, so
this is behaviour-preserving. The DM compose button now also gets the channel
list's border (and its always-reset-to-LIGHT), folding in the earlier
[+ send] visibility fix.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>