Build out documentation (use cases, implementation guidance, worked examples)

This is an older one, but brought up by PRC reviewer Matt Brush, who flagged that the repository's documentation doesn't yet cover:
(1) use cases,
(2) what implementation looks like in practice,
(3) implementation guidance for adopters,
(4) worked examples, or
(5) future plans for expanding the spec, in an accessible way.

Minimal fix: link the existing slide deck and presentation recording from the README.
Better fix: build a small, focused documentation hub covering all five points outside the raw GitHub Markdown files.
Already tracked as GitHub Issue #19 - this exists mainly to flag it as a live priority on the board.

Start with the README and review the existing slide deck and presentation recording, which are identified as the minimal documentation fix. For the broader option, use GitHub Issue #19 as the active tracking point and define a focused documentation hub covering use cases, implementation practice, adopter guidance, worked examples, and future plans. Done means the requested material is accessible outside the raw Markdown files.

Written by the indexing model from the issue text.