Bumps `@version` to 0.8.0, assembles the two pending changelog
fragments into a `## [0.8.0]` section, deletes them in the same commit
per changelog.d/README.md, and moves both install pins to `~> 0.8` -
README.md's and the one in docs/ops-embedding.md that step B of the
release recipe names.

A minor: the expression editor takes a `path_types` assign that decides
a clause's operator list and value control from the declared kind
(sui-2vj), and the expression field's two mode switches stop rendering
run-together on a host page with no stylesheet (sui-aln). The trace
wire format is untouched - version 1, 25 types - so a consumer taking
`~> 0.8` re-pins nothing.

Every bullet is verbatim from its fragment, grouped by heading in the
Added/Fixed order step A.3 names; the lead paragraph is the only prose
written at release time. No link-reference block, per step A.4. The
section carries the commit's own local date, in the separator-free form
every prior section uses.

Refs: sui-oyy