v0.4.0 — verification pass, register, and a fingerprint gate

Three of the forty-two prompts in this library have been run against a real
codebase. This release publishes the process behind that, including the parts
of the process that went wrong.

What "verified" means, exactly: the prompt was run against a real codebase
and the run produced anti-patterns it did not already contain. It is not a
score, and a prompt nobody has run is not a suspect one.

Verified (3):

• platform-engineering — two Kubernetes repositories, an earlier pass
• backend-services — production code where many services implement one contract
• data-platforms — a private production system whose data path is an
  operational streaming plane rather than a warehouse

The other thirty-nine have not been run, and each is named individually in
the register so the absence is on the record rather than inferred from a
summary. jvm-backend is the one not simply waiting on time: no codebase with a
JVM service layer was available to run it against, and its row says that.

Two caveats worth more than the tick. data-platforms was run against a
streaming system, so the warehouse half of that prompt — columnar storage, file
formats, compaction, query plans, per-dataset cost — has no evidence behind it,
and nothing was written about it. The absence of findings there is not coverage.
And platform-engineering's corpus was public rather than private, which is a
different kind of evidence.

Also in this release

• docs/verification.md — a register with one row per prompt
• docs/worked-example.md — one prompt end to end, including what it got wrong
• A Verified column in the generated index, so a reader can tell at a glance
• check_no_fingerprint.py — CI now fails if a committed file names a private
  codebase. It catches names, paths, and commit hashes; it does not catch
  magnitudes, and that limit is documented rather than hidden

The findings were derived from a private system and are published in generalised
form. No name, path, count, or product from that codebase appears in this
repository or its history.

Full detail in CHANGELOG.md.