Agentcore harness unable to load skills https://github.com/awslabs/agentcore-samples/tree/main/01-features/01-harness/01-advanced-examples/05-agent-skills

## Summary
I was trying https://github.com/awslabs/agentcore-samples/tree/main/01-features/01-harness/01-advanced-examples/05-agent-skills but in oetl_logs I could see agentcore harness was unable to load skills/xlsx

## Details
Followed the steps in the tutorial. " "command": "ls -la .agents/skills/xlsx/ 2>/dev/null && echo 'skill directory OK' || echo 'skill not found'"" command gave me skill directory ok but in logs I could see it failed to load it.

```
2026-05-27T19:17:28.123Z2026-05-27 19:17:27,974 WARNING [strands.vended_plugins.skills.agent_skills] [agent_skills.py:334] [trace_id=xxx span_id=xx resource.service.name=harness_SkillsDemo_xxxx.DEFAULT trace_sampled=True] - path= \| skill source path does not exist, skipping

  | 2026-05-27T19:17:28.124Z2026-05-27 19:17:28,124 WARNING [strands.vended_plugins.skills.agent_skills] [agent_skills.py:110] [trace_id=xxxx span_id=xxx resource.service.name=harness_SkillsDemo_xxx.DEFAULT trace_sampled=True] - no skills were loaded, the agent will have no skills available
```

## Expected Behavior
agentcore strands harness should be able to load the skills