Put the workaround back where the container is not the mesh's

The mesh gives its names to the containers it declares. This one is started by
the test with `docker run` — nothing declared it, so nothing configured it, and
removing the workaround here was claiming a reach the change does not have.

The boundary is the right one: a container somebody runs by hand is not the
mesh's to configure. Reaching into every container on a machine, declared or
not, is what a resolver in resolv.conf would be for — and that remains the
case for wanting one.

The proof that names work inside containers is its own test, against a
container the mesh declared, and it passes.

test/integration/mesh.test.ts

@@ -816,14 +816,23 @@ test("rotating a credential moves both ends, and the old one stops working", {
   // As the role the provisioner made, into the database it made. The provisioner names a role
   // after the machine and a database after what the module asked for — which is the contract, and
   // getting it wrong here made the test fail against a provisioner that had done its job.
-  // **By name, from inside the container.** This used to resolve the address on the machine and
+  // By address, resolved on the machine.
-  // pass it in, because a container does not inherit its host's /etc/hosts and the name failed as
+  //
-  // "could not translate host name" — which reads like a mesh that never wrote the name. The mesh
+  // **This container is not the mesh's.** The mesh gives its names to the containers it declares,
-  // now gives every container the names it knows, so the workaround is gone and its absence is
+  // and this one is started by the test with `docker run` — nothing declared it, so nothing
-  // the assertion.
+  // configured it. That boundary is the right one: a container somebody runs by hand is not the
+  // mesh's to configure, and reaching into every container on a machine is what a resolver in
+  // resolv.conf would be for.
+  //
+  // So the workaround stays here, and the proof that names work inside containers is its own
+  // test, against a container the mesh declared.
+  const where = (await must("laptop",
+    `getent hosts anchor.internal | head -1 | cut -d' ' -f1`)).trim();
+  assert.match(where, /^[0-9.]+$/, `the mesh's name for anchor does not resolve here: ${where}`);
+
   const login = async (password: string) =>
     await on("laptop", `docker run --rm -e PGPASSWORD=${quote(password)} ` +
-      `${pinned("postgres")} psql -h anchor.internal -p 5433 -U mesh_laptop ` +
+      `${pinned("postgres")} psql -h ${where} -p 5433 -U mesh_laptop ` +
       `-d realapp -qAt -c "select 1"`, 120_000);
 
   const diagnostics = async () =>