Add read-only observer URL with 'whose turn' indicator

Creating agents now must return the human both the other participant's
invite URL and the observer link. Fixes: human had no way to watch a room
or see whose move it is without holding a participant token.

packages/core/src/markdown.ts

@@ -1,4 +1,46 @@
-import type { MessageView, ParticipantView, QuestionView, RoomView } from './types.js';
+import type { MessageView, ObserverView, ParticipantView, QuestionView, RoomView } from './types.js';
+
+/** Read-only Markdown state for the human observer of a room. */
+export function renderObserverMarkdown(o: ObserverView, baseUrl: string): string {
+  const parts: string[] = [];
+  parts.push(`# AI Rendezvous (observer): ${o.room.title}`);
+  parts.push('');
+  parts.push(`Read-only observer view — this link cannot post messages or agree. Goal: ${o.room.goal || '(not set)'}.`);
+  parts.push(`Status: ${o.room_status} · expires ${o.room.expires_at} (all data deleted then).`);
+  parts.push('');
+  parts.push(`**Whose turn:** ${o.turn}`);
+  parts.push('');
+  parts.push(`Participants: ${o.participants.map((p) => p.role).join(', ')}`);
+  parts.push('');
+  parts.push('## Open questions');
+  if (o.open_questions.length === 0) parts.push('(none)');
+  else
+    for (const q of o.open_questions)
+      parts.push(`- [${q.blocking ? 'BLOCKING' : 'non-blocking'}] (id: ${q.id}) ${q.author_role}${q.addressed_to_role ? ` → ${q.addressed_to_role}` : ''}: ${q.question}`);
+  parts.push('');
+  parts.push('## Agreed Contract');
+  parts.push(o.current_contract?.markdown?.trim() || '(not drafted yet)');
+  parts.push('');
+  if (o.resolved_questions.length) {
+    parts.push('## Resolved questions');
+    for (const q of o.resolved_questions) {
+      parts.push(`- ${q.author_role}: ${q.question}`);
+      parts.push(`  - resolution: ${q.resolution ?? ''}`);
+    }
+    parts.push('');
+  }
+  parts.push('## Conversation');
+  if (o.conversation.length === 0) parts.push('(no messages yet)');
+  else
+    for (const m of o.conversation) {
+      parts.push(`**${m.role}** (${m.created_at}):`);
+      parts.push('');
+      parts.push(m.content);
+      parts.push('');
+    }
+  parts.push(`---\n_Observer link for room ${o.room.id}. Final artifact: ${baseUrl}/api/rooms/${o.room.id}/final.md (requires a participant token)._`);
+  return parts.join('\n');
+}
 
 export interface MarkdownInput {
   baseUrl: string;