docs: align demo evidence and footer

[abrichr]

What changed

• connects the docs homepage and qualification appendix to the public real-application demo and exact OpenEMR evidence viewer
• uses the shared visible vocabulary: Recorded demonstration, Compiled replay, Guided view, Raw footage, VERIFIED, and HALTED
• explains that guided target geometry appears only when bound to an exact decoded replay frame, while raw evidence media stays unchanged
• aligns the Desktop overlay guide with the same post-composed presentation contract
• defines Material footer foreground tokens explicitly in light mode and raises the copyright text from 0.64rem to 0.72rem

Why

Web, Cloud, Desktop, and docs should explain one visual contract. The docs previously described the runtime overlay without linking to the public end-to-end experience, while Material's footer retained dark-footer foreground defaults and undersized metadata even on the warm light background.

Verification

• UV_CACHE_DIR=/tmp/uv-cache-openadapt-ops-docs uv run mkdocs build --strict
• UV_CACHE_DIR=/tmp/uv-cache-openadapt-ops-docs uv run pytest -q (76 passed)
• git diff --check
• headless Chrome screenshots at 1440px of the homepage demo/evidence block and a short page footer
• both public demo and exact-evidence links return HTTP 200

Screenshots:

• /private/tmp/openadapt-docs-local-home.png
• /private/tmp/openadapt-docs-local-footer.png