v0.16.18 (and every release back to v0.16.7) failed at the build
matrix because the aarch64-unknown-linux-gnu job OOM-killed the
runner during link (~1h, "hosted runner lost communication"). The
publish gate is `needs: build`, so no GH release has been published
since v0.16.6 and Homebrew's on_linux/on_arm block has been pinned
to v0.16.6 for ~a week.

The previous commit (842aba399c) added an 8 GB swapfile + memory-
budget RUSTFLAGS for the aarch64-linux-gnu matrix entry, but
`gh run rerun --failed` re-runs jobs using the workflow file at the
tag's commit — not main — so v0.16.18 cannot pick up that fix. A
new tag on top of the patched release.yml is the cleanest non-
destructive path to exercise the new link-time memory budget.

No code changes vs. v0.16.18. Just the 8 standard version-string
bumps (Cargo.toml + Cargo.lock + 2 man pages + 3 docs HTMLs + 1
demo example) that the meta cargo-doc-version-sync and man-page-
version-sync gates require for the version to publish cleanly.