fix(tool-ui): suffix agent-artifact downloads with version label

For multi-version artifacts, the download filename was memoized on
title + artifactType + language only, so each version saved with the
same name and silently overwrote prior downloads. Suffix the slug
with the active version label when more than one version exists;
single-version artifacts keep their existing filename.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: NickB03

components/tool-ui/agent-artifact/agent-artifact.test.tsx

@@ -61,7 +61,7 @@ describe('AgentArtifact', () => {
     expect(screen.getByText('120 tokens')).toBeInTheDocument()
     expect(
       screen.getByRole('link', { name: 'Download artifact content' })
-    ).toHaveAttribute('download', 'component-spec.md')
+    ).toHaveAttribute('download', 'component-spec-version-2.md')
   })
 
   it('handles denied clipboard writes without surfacing an unhandled rejection', async () => {

components/tool-ui/agent-artifact/agent-artifact.tsx

@@ -114,15 +114,22 @@ function parseTable(content: string) {
   return parseMarkdownTable(content) ?? parseCsvTable(content)
 }
 
+function slugify(value: string) {
+  return value
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, '-')
+    .replace(/^-|-$/g, '')
+}
+
 function getDownloadFilename(
   title: string,
   artifactType: string,
-  language?: string
+  language?: string,
+  versionLabel?: string
 ) {
-  const slug = title
-    .toLowerCase()
-    .replace(/[^a-z0-9]+/g, '-')
-    .replace(/^-|-$/g, '')
+  const titleSlug = slugify(title) || 'artifact'
+  const versionSlug = versionLabel ? slugify(versionLabel) : ''
+  const slug = versionSlug ? `${titleSlug}-${versionSlug}` : titleSlug
   const extension =
     artifactType === 'table'
       ? 'csv'
@@ -132,7 +139,7 @@ function getDownloadFilename(
           ? 'ts'
           : 'txt'
 
-  return `${slug || 'artifact'}.${extension}`
+  return `${slug}.${extension}`
 }
 
 export function AgentArtifact({
@@ -174,9 +181,12 @@ export function AgentArtifact({
     () => `data:text/plain;charset=utf-8,${encodeURIComponent(activeContent)}`,
     [activeContent]
   )
+  const downloadVersionLabel =
+    versions && versions.length > 1 ? activeVersion?.label : undefined
   const downloadFilename = useMemo(
-    () => getDownloadFilename(title, artifactType, language),
-    [artifactType, language, title]
+    () =>
+      getDownloadFilename(title, artifactType, language, downloadVersionLabel),
+    [artifactType, downloadVersionLabel, language, title]
   )
   const Icon = artifactIcons[artifactType]