Replace the background-clarify toast (expired on alt-tab, easy to miss) with a
persistent, glowing amber "needs input" dot on the session's sidebar row,
driven off a new ClientSessionState.needsInput flag mirrored into a
$attentionSessionIds store. The flag is set on clarify.request and cleared the
moment the turn resumes (tool.complete) or ends.
Also: redesign the clarify tool UI (borderless choices, pseudo-radio dots,
right-aligned checkmark, arc border, tighter padding), make Button the single
source of icon-button styling (4px radius, new icon-titlebar variant, titlebar
buttons rendered polymorphically via asChild, Codicons throughout), put the
file-tree refresh action first, and .trim() pasted composer text.