docs/install/clawdock.md: renamed '## Related pages' to '## Related'
for consistency with sibling install docs and converted the 3-bullet
list into a CardGroup linking docker, docker-vm-runtime, and updating.
docs/install/nix.md: replaced 2 typography characters with ASCII
equivalents and converted the 3-bullet Related list into a CardGroup,
adding an Updating card so readers wiring nix-openclaw next to a
managed install see the upgrade path.
docs/concepts/features.md: converted the 2-bullet Related list into a
CardGroup, adding cross-links to channels and plugins so the page now
points readers at both deeper concepts (experimental features, agent
runtime) and direct surfaces (channels, plugins).
docs/tools/pdf.md: replaced 2 typography characters with ASCII
equivalents.
