Judge tests that read another repository against what the check clones, never the desktop's checkout (issue 432)

Tests that read ../../../mesh-catalog or ../../../mesh-host gave a verdict
that depended on what sat beside the checkout: a stale or dirty sibling
failed them on a desktop, and a missing one skipped them unseen. They now
read the clone the build seat puts in MESH_CHECK_BESIDE, failing when it is
absent there, and elsewhere a copy captured at a named commit.

The skip had hidden that the builder test read a module retired by ADR 0190.
The systemd reading test no longer counts the machine's own environment.d.

testdata/beside/CAPTURED

@@ -0,0 +1,18 @@
+What a test reads of another repository when no merge check has cloned it beside this one (internal/beside,
+novox/hq issue 432). Copied from the repositories at the commits below, never written by hand. Each
+module.json is kept as module.json.captured: a module.json in this repository is a module of it to the
+forge and the planner, and a merge would build and register it.
+
+mesh-catalog  b9de001833b1b61b297182b8e3bcdae1cbdeace9  modules/*/module.json, modules/nats/Dockerfile
+mesh-host     bd5cc6980419c1bd4824be6d58dfebd2381a9de3  examples/foundation-first-node-nats.lock
+
+To move them, from this repository's root, with the two repositories checked out beside it:
+
+  rm -rf testdata/beside/mesh-catalog testdata/beside/mesh-host
+  mkdir -p testdata/beside/mesh-catalog testdata/beside/mesh-host
+  git -C ../mesh-catalog archive <commit> modules | tar -x -C testdata/beside/mesh-catalog --wildcards \
+    'modules/*/module.json' 'modules/nats/Dockerfile'
+  find testdata/beside -name module.json -exec mv {} {}.captured \;
+  git -C ../mesh-host archive <commit> examples/foundation-first-node-nats.lock | tar -x -C testdata/beside/mesh-host
+
+and write the commits here.