feat: show draft preset chips under the welcome message on mobile/vscode

On narrow surfaces (mobile, vscode) the composer sits at the bottom and
only the welcome message is centered, so the preset chips had nowhere
sensible to live and were desktop-only. Render them under the centered
welcome message there instead.

Extract the shared preset list (draftPresets.ts) and chip row
(DraftPresetChips) so both layouts reuse them. Since the command-aware
submit lives in ChatInput, ChatContainer triggers it through a new
input-store channel (requestPresetSubmit / consumePendingPresetSubmit)
that ChatInput consumes. Mini-chat stays excluded — too small for the row.

packages/ui/src/components/chat/ChatContainer.tsx

@@ -2,6 +2,8 @@ import React from 'react';
 import type { Message, Part, Session } from '@opencode-ai/sdk/v2';
 
 import { ChatInput } from './ChatInput';
+import { DraftPresetChips } from './DraftPresetChips';
+import { useInputStore } from '@/sync/input-store';
 import { useUIStore } from '@/stores/useUIStore';
 import { Skeleton } from '@/components/ui/skeleton';
 import ChatEmptyState from './ChatEmptyState';
@@ -811,7 +813,7 @@ export const ChatContainer: React.FC<ChatContainerProps> = ({ autoOpenDraft = tr
 		return (
 			<div className="relative flex h-full flex-col bg-background transform-gpu">
 				{useCompactDraftLayout && !isDesktopExpandedInput ? (
-					<div className="flex min-h-0 flex-1 items-center justify-center px-6 text-center">
+					<div className="flex min-h-0 flex-1 flex-col items-center justify-center px-6 text-center">
 						<h1 className="text-balance text-3xl font-normal tracking-tight text-foreground">
 							{renderDraftTitle(
 								draftProjectLabel
@@ -820,6 +822,12 @@ export const ChatContainer: React.FC<ChatContainerProps> = ({ autoOpenDraft = tr
 								draftProjectLabel,
 							)}
 						</h1>
+						{chatSurfaceMode !== 'mini-chat' ? (
+							<DraftPresetChips
+								onSubmit={(text) => useInputStore.getState().requestPresetSubmit(text)}
+								className="mt-8 max-w-md"
+							/>
+						) : null}
 					</div>
 				) : null}
 				<div