Branch model corrections: wilm is an active sibling branch

Also stops wj-status offering to promote work that already landed.

CONTRIBUTING.md

@@ -153,9 +153,15 @@ Tests are required for:
 
 ## Branches: what belongs on main, and what does not
 
-Two branches. `main` is the product every site runs and the publication mirror
-exports. `<site>` branches - currently `wj` - hold work that is not ready for
-other sites to see.
+`main` is the product every site runs and the publication mirror exports.
+`<site>` branches hold work that is not ready for other sites to see. There are
+two: `wj` here, and `wilm` on the corporate GitHub, where the other site
+develops the .NET endpoint agent.
+
+A site branch is not a fork. Both feed `main`, and the sooner they do it the
+cheaper it is. A branch the dev box cannot see is still a branch: `wilm` is not
+visible from here because this machine has no GitHub account, which is why
+`fetch-wilm-branch.cmd` on the share exists to bring it back for review.
 
 **Most work is product.** ADR-015 gives site differences three homes on `main`:
 a setting with a neutral default, seed data, or a site-namespaced directory
@@ -188,10 +194,9 @@ quietly becomes the product.
 
 **The failure to watch for is not what you think.** Promoting something
 site-specific by accident is caught by the ADR-015 gate on the way into `main`.
-The real risk is product work sitting on a site branch forever because nobody
-decided - which is how the `wilm` branch stopped being a merge and became a
-port, costing a MySQL dialect fix, a contract violation and a plugin install to
-bring back.
+The real risk is product work sitting on a site branch until bringing it back is
+a port rather than a merge - one such round trip cost a MySQL dialect fix, a
+contract violation and a plugin install.
 
 So rebase the site branch on `main` often, and promote as you go rather than in
 one batch at the end.