docs: stop publishing internal references to a public wiki

docs/ is excluded from the code bundle and its scrub gate, because it goes to
the GitHub wiki instead - via a generator that has no gate at all. So the one
part of the repository written in prose, by people, about internal
infrastructure, was the one part nothing checked.

What was reaching a public wiki: the internal git server's URL and hostname,
.gitea workflow paths, developer home directories in the GE-Enforce cutover
reference, and a dev database root password inside a copy-pasteable command in
the import guide.

All replaced with neutral equivalents. tests/test_docs_publishable.py is now the
gate, at the source, in CI - a wiki page cannot be un-published, so catching this
after the fact is not good enough.

PROJECT-REVIEW.md also referred to internal tooling by name throughout; those
references are generalised. It remains an internal candid assessment of this
project that is nonetheless published, which is worth a separate decision.

docs/IMPORT-API.md

@@ -497,7 +497,7 @@ need it to remap foreign keys (a machine's `businessunitid`, a checkout's
 After each phase, compare counts. Legacy side (read-only), for example:
 
 ```bash
-docker exec dev-mysql mysql -uroot -prootpassword prodscratch \
+docker exec dev-mysql mysql -uroot -p"$MYSQL_ROOT_PASSWORD" prodscratch \
   -e "SELECT COUNT(*) FROM vendors;"
 ```