fix(wcm): remove six dead links from the public launch page - #41

Every link from agentrust-io.com/wcm/ into the WCM repository 404s. The
repository is private, and a launch page's entire audience is anonymous
readers, so all six were broken for exactly the people the page is for:

  /blob/main/THREAT-MODEL.md   "Full threat model"
  /issues/78 and /issues/79    the two disclosed open limitations
  /issues                      "Review open questions", for security researchers
  /actions                     the "574 tests passing" evidence claim
  /tree/main/conformance/vectors  the "91 conformance vectors" claim

This is the same trap agentrust-io/integrations#141 made a hard CONTRIBUTING
rule about, arriving from the other direction: fourteen integration READMEs now
point here as "specification and documentation", so a reader following one to
find the spec landed on a page whose own links were dead.

Each replacement is a real destination rather than a redirect of the problem:

  Vectors and test count now point at PyPI, and say why in a title attribute.
  Both are checkable from the published package, because the sdist ships tests/
  and the conformance vectors. That is a stronger claim than a CI badge: a
  reader can reproduce the numbers instead of being shown a green tick.

  The two limitations lose their hyperlinks and keep their prose. The paragraph
  already states both in full; the disclosure was always the point and the link
  only ever pointed into a tracker nobody outside the org can open.

  "Full threat model" points at the on-page limits section, which is the public
  statement of the same thing.

  Security researchers get a mailto, matching the two personas that already use
  one. An issue tracker they cannot open is not a way in.

The evidence strip had also drifted: pinned at a pre-0.27.0 commit, showing
0.26.0 and 574 tests. Now a952cb6, 0.27.0 and 599, with proof.json regenerated
from that commit.

launch-page.test.js gains the durable part. It previously asserted the issue
LINKS were present, which is how these survived: the check enforced the dead
link rather than the disclosure. It now asserts the limitation prose, and
separately that no link into the private repository exists anywhere on the
page. Verified it fails on a reintroduced link. Delete that check when the
repository goes public (weight-custody-manifest#40).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014NL8o3PXq6kfs2SdmBv6ak