Cut the README down to what a reader needs

[tonytonycoder11]

The README was 702 lines and about two hundred of them were not about using this library. It is 555 now
and nothing a reader needs was cut.

The Roadmap section

Three paragraphs of version history, one per release, growing by one every time something ships. That
is CHANGELOG.md restated in prose, which is the failure mode the one-home rule exists to prevent: two
descriptions of the same release, only one of which anybody updates.

The section is now four sentences. The plan is on the board, what shipped is in the changelog, what a
version may change is in STABILITY.md, and each of the three is linked.

Three places that told a story instead of a fact

The footprint table was followed by four paragraphs on the discovery that the GraalVM claim had never
been tested and what building the image turned up. The architecture tree by four on what adding the
second engine proved about the seam. The platforms section argued the Kotlin/JS exclusion, and then
## Architecture argued it again from a different premise, so the two no longer agreed with each other.

What survives of each is the fact and the link that makes it checkable. The GraalVM row keeps its link
to the CI job that produces the 37 ms, because a number nobody can check is worse than no number.

Smaller cuts

The status blockquote was a nine-line feature inventory, and nobody reads an inventory to decide whether
to depend on something; it names what the client covers and points at the board. Scrolling, deleting,
counting and retrieving were four headings for four one-line calls and are one. Tracing and metrics
were one section and a missing one, and are now Observability.

Two links repointed

benchmarks/README.md and docs/migrating-from-qdrant-client.md both linked
#footprint-vs-the-official-client, which is now #compared-with-the-official-client. Fixed here
rather than left to 404.

audit-library.sh reports the repository at standard, with the section order, the status blockquote and
the shipped-state vocabulary all intact.

[trueup-by-nacode-studios]

This pull request adds no capability the code did not already have.

_{3 files read · 3134 ms · against d696444}