fix(brain): resolve create parent sections

[golemcore1]

Summary

• Resolve create_page parent_path through Brain before creating the page.
• Try the exact parent path first, then a slugified title/path fallback so inputs like golem notes can resolve to golem-notes.
• Reject parent paths that resolve to Brain pages instead of sections with a clear error.
• Return cleaner Brain API errors by extracting error/message fields instead of exposing raw JSON response bodies.
• Update the Brain tool schema description and add unit tests for exact lookup, slug fallback, page-as-parent rejection, missing sections, and API error formatting.
• Bump the golemcore/brain plugin metadata to 1.0.2 and add the registry/golemcore/brain/versions/1.0.2.yaml release descriptor so the fix can be published correctly.