Add comprehensive research timeline (STO-REF-0011) tracing intellectual
evolution from SyDigital through Tractatus to sovereign governance.
Add sidebar filter UI to docs page (document type + audience dropdowns
with URL parameter support). Extend Document model with document_type
and status fields in create method and summary projection.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
