[BUG] User Id is not passed to the AgentCore Runtime - Agent

**Describe the bug**
User Id / Actor Id is not available in the Agent when agent invoke is run by passing --user-id

**To Reproduce**
Steps to reproduce the behavior:
1. Run Agent in local mode - agentcore launch -l
2. Invoke Agent with ``` agentcore invoke '{"prompt": "do you remember me and my likings"}' -l --user-id user1 --session-id session1
3. I see session id being populated in Context Object but I do not see User Id in Payload or Context

**Expected behavior**
User Id should be present in payload or context when agent is invoked with --user-id

**Error Output**
```
Paste any error messages or stack traces here
```

**Environment:**
- OS: [e.g. Ubuntu 22.04, macOS 13.0, Windows 11]
- Python version: [e.g. 3.10.5]
- Package version: [e.g. 0.1.0]
- Installation method: [pip, conda, from source]

**Additional context**
This impacts the use of AgentCore Memory as memory namespaces that need ActorId will not work

Start by tracing the local `agentcore invoke` path with `--user-id` and `--session-id`, then inspect how the AgentCore Runtime payload and context are assembled. Confirm where the session ID is propagated and add equivalent propagation for the user or actor ID; verify that the ID is available to the agent and supports AgentCore Memory namespaces.

Written by the indexing model from the issue text.