Rename docs/gigafactory/ to docs/GIGAFACTORY/ and update the cross-repo
source-of-truth references in the fleet README and types.ts comment. Add an
index README listing the platform docs and pointing to the canonical spec in
learning_ai_devops_tools. Docs/comment only; no behavior change.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
