refactor: extract agent bounded context + fix SSE comments + cleanup unused

- Extract src/lib/agent/ bounded context with types, registry, messaging
- Add comments_count to BeadIssue for SSE comment detection
- Create batch endpoints for mail/reservations APIs
- Add memory validation to session-preflight
- Remove unused empty dirs (mockup, sessions, timeline)
- Move stashes to docs/references, gitignore them

src/app/api/agents/reservations/batch/route.ts

@@ -0,0 +1,33 @@
+import { NextResponse } from 'next/server';
+import { statusAgentReservations } from '../../../../../lib/agent-reservations';
+
+export const dynamic = 'force-dynamic';
+
+export async function GET(request: Request): Promise<Response> {
+  const { searchParams } = new URL(request.url);
+  const agentsParam = searchParams.get('agents') ?? '';
+  
+  if (!agentsParam) {
+    return NextResponse.json({ ok: true, data: [] }, { status: 200 });
+  }
+  
+  const agentNames = agentsParam.split(',').map(a => a.trim()).filter(Boolean);
+  
+  const results = await Promise.all(
+    agentNames.map(async (agent) => {
+      const result = await statusAgentReservations({ agent });
+      if (!result.ok || !result.data) {
+        return { agent, scope: undefined, reservations: [] };
+      }
+      const reservations = result.data.reservations ?? [];
+      const first = reservations[0];
+      return { 
+        agent, 
+        scope: first?.scope as string | undefined, 
+        reservations 
+      };
+    })
+  );
+  
+  return NextResponse.json({ ok: true, data: results }, { status: 200 });
+}