feat(desktop): persistent needs-input indicator + icon button consolidation

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.

apps/desktop/src/app/session/hooks/use-session-state-cache.ts

@@ -4,7 +4,7 @@ import { type MutableRefObject, useCallback, useEffect, useRef } from 'react'
 import type { ChatMessage } from '@/lib/chat-messages'
 import { preserveLocalAssistantErrors } from '@/lib/chat-messages'
 import { createClientSessionState } from '@/lib/chat-runtime'
-import { $busy, $messages, noteSessionActivity, setSessionWorking } from '@/store/session'
+import { $busy, $messages, noteSessionActivity, setSessionAttention, setSessionWorking } from '@/store/session'
 
 import type { ClientSessionState } from '../../types'
 
@@ -152,7 +152,12 @@ export function useSessionStateCache({
         setSessionWorking(previous.storedSessionId, false)
       }
 
+      if (previous.storedSessionId !== next.storedSessionId || !next.needsInput) {
+        setSessionAttention(previous.storedSessionId, false)
+      }
+
       setSessionWorking(next.storedSessionId, next.busy)
+      setSessionAttention(next.storedSessionId, next.needsInput)
       // Every state update is effectively a "still alive" heartbeat for
       // streaming events. The session-store watchdog uses this to keep the
       // working flag alive during long-running turns and to clear it once