docs: restructure into rfc-app 'docs' collection (Maker Collective)

Move the two Maker Platform memos into docs/rfcs/ with minimal entry
frontmatter (slug/title/state) and add docs/.collection.yaml (type:
document, public) so the rfc-app registry mirror surfaces them as the
'docs' collection of the new maker-collective project.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/.collection.yaml

@@ -0,0 +1,4 @@
+# §22.4a collection manifest — read by the registry mirror.
+type: document
+visibility: public
+name: Docs