refactor(app): consolidate seeds into single conversation

All 15 seed prompts now load as one conversation ("Content Showcase")
instead of 15 separate ones. /seed collapses chat to show PromptIndex
so users can quickly pick any prompt to see its content surface.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/__tests__/fixtures/seedPrompts.ts

@@ -438,30 +438,31 @@ One of each is all you need to start.`,
 /**
  * Convert seed prompts to the .dev/chats.json conversation format.
  */
-export function seedPromptsToConversations(): Record<string, {
+/** Build a single conversation with all seed prompts as sequential messages. */
+export function seedPromptsToConversation(): {
   id: string
   title: string
   messages: { id: string; role: string; content: string; timestamp: number }[]
   createdAt: number
   updatedAt: number
-}> {
-  const conversations: Record<string, any> = {}
-  const baseTime = 1772488800000 // Stable base timestamp
+} {
+  const baseTime = 1772488800000
+  const messages: { id: string; role: string; content: string; timestamp: number }[] = []
 
   for (let i = 0; i < seedPrompts.length; i++) {
     const seed = seedPrompts[i]
     const ts = baseTime + i * 60000
-    conversations[seed.id] = {
-      id: seed.id,
-      title: seed.userQuery.slice(0, 60),
-      messages: [
-        { id: `${seed.id}-q`, role: 'user', content: seed.userQuery, timestamp: ts },
-        { id: `${seed.id}-a`, role: 'assistant', content: seed.assistantResponse, timestamp: ts + 3000 },
-      ],
-      createdAt: ts,
-      updatedAt: ts + 3000,
-    }
+    messages.push(
+      { id: `${seed.id}-q`, role: 'user', content: seed.userQuery, timestamp: ts },
+      { id: `${seed.id}-a`, role: 'assistant', content: seed.assistantResponse, timestamp: ts + 3000 },
+    )
   }
 
-  return conversations
+  return {
+    id: 'seed-all',
+    title: 'Content Showcase',
+    messages,
+    createdAt: baseTime,
+    updatedAt: baseTime + seedPrompts.length * 60000,
+  }
 }