sidebar redesign + markdown typography overhaul
Sidebar: increase glass opacity (0.92/0.88), flat conversation rows
instead of pill shapes, 3-dot context menu (rename/delete/pin/lock),
smaller profile avatar (30dp), logout integrated into user card.
Add KaizenApi.patchConversation + deleteConversation for CRUD.
Markdown: increase line-height from 23sp to 26sp (×1.625 ratio),
double paragraph spacing (6dp→12dp), generous heading margins
(18dp top, 8dp bottom), wider list item spacing — matches Gemini-
level readability.
f3d8154052