feat(config): add subagent_tools to complement primary_tools

[spoons-and-mirrors]

What does this PR do?

feat: Adds subagent_tools to the experimental config to allow specifying tools that should only be available to subagents, complementing primary_tools

refactor: moved the primary_tools filtering to the tool registry for consistency (as subagent_tools needs to be constructed at the registry level)

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

I found a potentially related PR that may be relevant to your feature:

Related PR:

• fix: prevent subagent permission bypass via tools field inheritance #7473 - fix: prevent subagent permission bypass via tools field inheritance

This PR addresses subagent tool permissions and inheritance, which is conceptually related to your PR that adds subagent_tools configuration. They may be complementary or address overlapping concerns around controlling which tools are available to subagents.

Otherwise, no other duplicate PRs found with the specific subagent_tools and primary_tools terminology.

[spoons-and-mirrors]

unrelated