v2 phase 4+5: Discord via Chat SDK, expanded MCP tools, message seq IDs

- Chat SDK bridge + Discord adapter (gateway listener, message routing)
- MCP tools refactored into modular structure: core (send_message, send_file,
  edit_message, add_reaction), scheduling (schedule/list/cancel/pause/resume
  tasks), interactive (ask_user_question, send_card), agents (send_to_agent)
- Message seq IDs: shared integer sequence across messages_in/out so agents
  see small numeric IDs instead of platform snowflakes
- busy_timeout=5000 for session DB (poll loop + MCP server concurrent access)
- Always copy agent-runner source to fix stale cache when non-index files change
- Seed script for Discord testing, e2e test script

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

container/agent-runner/src/mcp-tools/agents.ts

@@ -0,0 +1,58 @@
+/**
+ * Agent-to-agent MCP tools: send_to_agent.
+ */
+import { writeMessageOut } from '../db/messages-out.js';
+import type { McpToolDefinition } from './types.js';
+
+function log(msg: string): void {
+  console.error(`[mcp-tools] ${msg}`);
+}
+
+function generateId(): string {
+  return `msg-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+}
+
+function ok(text: string) {
+  return { content: [{ type: 'text' as const, text }] };
+}
+
+function err(text: string) {
+  return { content: [{ type: 'text' as const, text: `Error: ${text}` }], isError: true };
+}
+
+export const sendToAgent: McpToolDefinition = {
+  tool: {
+    name: 'send_to_agent',
+    description: 'Send a message to another agent group.',
+    inputSchema: {
+      type: 'object' as const,
+      properties: {
+        agentGroupId: { type: 'string', description: 'Target agent group ID' },
+        text: { type: 'string', description: 'Message content' },
+        sessionId: { type: 'string', description: 'Target specific session (optional)' },
+      },
+      required: ['agentGroupId', 'text'],
+    },
+  },
+  async handler(args) {
+    const agentGroupId = args.agentGroupId as string;
+    const text = args.text as string;
+    if (!agentGroupId || !text) return err('agentGroupId and text are required');
+
+    const id = generateId();
+
+    writeMessageOut({
+      id,
+      kind: 'chat',
+      channel_type: 'agent',
+      platform_id: agentGroupId,
+      thread_id: (args.sessionId as string) || null,
+      content: JSON.stringify({ text }),
+    });
+
+    log(`send_to_agent: ${id} → ${agentGroupId}`);
+    return ok(`Message sent to agent ${agentGroupId} (id: ${id})`);
+  },
+};
+
+export const agentTools: McpToolDefinition[] = [sendToAgent];