ui: UI/chat form follow ups (#26743)

* ui: split the markdown rendering setting per surface

User content and thinking get their own toggle again, so turning off
markdown for a message leaves reasoning blocks formatted. Both default
to markdown. A stored renderContentAsRawText unfolds onto the user key
and is dropped from the config.

File mentions render as badges in the raw text path too, through a
narrow pass over [name](file://path) that leaves everything else
untouched.

* ui: let the rich chat input scroll past its max height

The contenteditable renderer caps its height with max-height but had no
overflow rule, so a long buffer overflowed into the input area wrapper
and got clipped by its overflow-hidden, leaving no way to reach the
bottom of the message. The textarea renderer scrolls natively and was
never affected.

* ui: apply the new lint and format config

* ui: move the render keys unfolding into the migration service

Address review from @allozaur: the settings store no longer rewrites
persisted config on load, the raw text toggle now unfolds onto the
per-surface render keys in migration.service.ts, next to the other
config migrations. The mention scanner flag and the directory path
suffix become named constants.

tools/ui/src/lib/components/app/chat/ChatForm/ChatFormContenteditable.svelte

@@ -797,7 +797,7 @@
 		data-placeholder={placeholder}
 		tabindex={disabled ? -1 : 0}
 		class={[
-			'chat-form-contenteditable text-md min-h-12 w-full whitespace-pre-wrap wrap-break-word border-0 bg-transparent p-0 leading-6 outline-none focus-visible:ring-0 focus-visible:ring-offset-0',
+			'chat-form-contenteditable text-md min-h-12 w-full overflow-y-auto whitespace-pre-wrap wrap-break-word border-0 bg-transparent p-0 leading-6 outline-none focus-visible:ring-0 focus-visible:ring-offset-0',
 			disabled && 'cursor-not-allowed'
 		]}
 		style="max-height: var(--max-message-height);"

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessage/ChatMessageSystem/ChatMessageSystem.svelte

@@ -164,7 +164,7 @@
 								? `max-height: ${MAX_HEIGHT}px;`
 								: 'max-height: none;'}
 						>
-							{#if !currentConfig.renderContentAsRawText}
+							{#if currentConfig.renderUserContentAsMarkdown}
 								<div bind:this={messageElement} class={isExpanded ? 'cursor-text' : ''}>
 									<MarkdownContent class="markdown-system-content" content={message.content} />
 								</div>

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessage/ChatMessageUser/ChatMessageUserBubble.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { ChatAttachmentsList, MarkdownContent } from '$lib/components/app';
+	import { ChatAttachmentsList, MarkdownContent, MentionText } from '$lib/components/app';
 	import { Card } from '$lib/components/ui/card';
 	import { config } from '$lib/stores/settings.svelte';
 	import type { DatabaseMessageExtra } from '$lib/types/database';
@@ -64,14 +64,14 @@
 		data-multiline={isMultiline ? '' : undefined}
 		style="{maxHeightStyle} overflow-wrap: anywhere; word-break: break-word;"
 	>
-		{#if renderMarkdown && !currentConfig.renderContentAsRawText}
+		{#if renderMarkdown && currentConfig.renderUserContentAsMarkdown}
 			<div bind:this={messageElement}>
 				<MarkdownContent class="markdown-user-content" {content} />
 			</div>
 		{:else}
-			<span bind:this={messageElement} class="text-md whitespace-pre-wrap">
-				{content}
-			</span>
+			<span bind:this={messageElement} class="text-md whitespace-pre-wrap"
+				><MentionText {content} /></span
+			>
 		{/if}
 	</Card>
 {/if}

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessageReasoningBlock.svelte

@@ -140,7 +140,7 @@
 		class:is-streaming={isPending}
 		onscroll={handleScrollEvent}
 	>
-		{#if !currentConfig.renderContentAsRawText}
+		{#if currentConfig.renderThinkingAsMarkdown}
 			<MarkdownContent content={section.content} class="text-muted-foreground" {attachments} />
 		{:else}
 			<div