fix: resolve session resumption issue by storing Claude's internal session ID

- Add discriminated union for agent options with proper type (claude)
- Store Claude's internal session ID separately from ACP session ID
- Use Zod schema validation for persisted agents
- Use correct session ID when resuming agents (Claude ID for Claude agents)
- Update to @boudra/claude-code-acp@0.8.1 which extracts Claude session ID

packages/server/package.json

@@ -18,7 +18,7 @@
   "dependencies": {
     "@agentclientprotocol/sdk": "^0.4.9",
     "@ai-sdk/openai": "^2.0.52",
-    "@boudra/claude-code-acp": "^0.8.0",
+    "@boudra/claude-code-acp": "^0.8.1",
     "@deepgram/sdk": "^3.4.0",
     "@modelcontextprotocol/sdk": "^1.20.1",
     "@openrouter/ai-sdk-provider": "^1.2.0",