Spec misalignment: ADK defines metadata.adk_additional_tools as list[str], but agentskills.io spec requires string values

[Satheesh-Balachandran]

Summary

There is a misalignment between Google ADK's implementation of SKILL.md metadata
and the agentskills.io specification,
which is causing the community skill validator to reject valid ADK skills.

What ADK defines

In src/google/adk/skills/models.py, the Frontmatter class defines:

metadata: dict[str, Any] = {}

For metadata.adk_additional_tools , should it turn into a space separated list instead of yaml list?