Add a create-rfc skill that directs agents through the OpenShell RFC process
and template. Expand the RFC template with clearer section guidance and
suggested lengths.
Signed-off-by: Kris Hicks <khicks@nvidia.com>
Each RFC now lives in its own folder (rfc/NNNN-short-name/) with
README.md as the main proposal. This gives each RFC room for diagrams,
images, and other supporting files without cluttering the top level.
Move 0000-template into the new layout and update rfc/README.md to
describe the convention.