press v2.3.1

A hardening release. Two output bugs are corrected -- a retail barcode that
crowded its quiet zone, and a cover commission that invented generic motifs
when the book named its subject only in prose -- and a latent hole in the
adapters boundary gate is closed, so the "one approved home for a subprocess"
invariant is now enforced by construction rather than held by luck. Three
verifier guards gain the known-bad fixtures that prove them, and the landing
page features Make Ready as the flagship book built end to end through the
press. Compatible within v2; no build changes a valid book's typography or
layout.

Changed

• The landing page features Make Ready as the flagship showcase -- a book
  taken end to end through the built-in facilities: a commissioned clothbound
  cover and fourteen engraved plates finished by press art enhance, the
  reader dressed in the book's own cloth, a subject index, registered ISBNs,
  and a table of authorities. It stands beside Mostly Done. as proof the
  pipeline makes real books, not just demos.

Fixed

• The retail cover barcode no longer crowds its quiet zone (#210). The
  EAN-13 symbol was drawn in a TikZ node whose default padding shifted it
  left, so the first guard bar read as ink inside the left quiet zone and
  verify-print refused an otherwise-correct wrap. The barcode node now sets
  inner sep=0 (matching the front-cover-art node), so the symbol sits exactly
  where the verifier's pixel model expects it. The integration cover-wrap
  fixture now carries a real print ISBN, so the quiet-zone check runs in CI.
• A cover commission draws the book's own subject instead of inventing
  one. When a book stated its subject only in description (or as a
  cover.emblem) and not as an explicit cover.subject, press cover fell
  back to the literal phrase "the book's subject" and the image model invented
  generic motifs. It now draws the subject from --subject, then
  cover.subject, then the book's description, then cover.emblem, and only
  then the literal -- so a book that says what it is about gets that on its
  cover.
• The adapters boundary gate no longer has a from-import blind spot. The
  gate that proves nothing outside press.adapters holds a direct subprocess
  or environment call matched only the subprocess.Popen attribute form; from subprocess import Popen and import subprocess as sp slipped past it, and
  the process controller's launcher did exactly that -- a real subprocess the
  gate reported as clean. The gate now flags the from-import binding of an
  executor and resolves aliased module imports, and the one production launcher
  has moved into press.adapters (its streaming sibling of SubprocessRunner)
  where a boundary call belongs, so the single-home invariant is enforced, not
  merely intended. Three verifier guards -- plate-link resolution, cover-wrap
  transparency, and barcode readability -- also gained the known-bad fixtures
  that give them teeth.