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/mesh-catalog/modules/feh/module.json.captured

@@ -0,0 +1,70 @@
+{
+  "module": "feh",
+  "version": "1",
+  "capabilities": [
+    "package-manager"
+  ],
+  "requires": [
+    "x11-display"
+  ],
+  "tools": [
+    "feh_set",
+    "feh_current"
+  ],
+  "shell": [
+    {
+      "for": "xinitrc",
+      "slot": "normal",
+      "code": "# The wallpaper (module feh, novox/hq ADR 0208): the declared one, set once per session.\n\"$HOME/.fehbg\"\n"
+    }
+  ],
+  "resources": [
+    {
+      "id": "package",
+      "type": "package",
+      "package": "feh"
+    },
+    {
+      "id": "wallpapers",
+      "type": "archive",
+      "path": "${machine:account-home}/.local/share/feh/wallpapers",
+      "owner": "${machine:account}",
+      "artifact": "wallpapers"
+    },
+    {
+      "id": "fehbg",
+      "type": "file",
+      "path": "${machine:account-home}/.fehbg",
+      "owner": "${machine:account}",
+      "mode": "0755",
+      "content": "#!/bin/sh\n# The wallpaper (module feh, novox/hq ADR 0208). Owned by the mesh: replaced at every push. The\n# session's start runs it, and so may anything that wants the declared wallpaper back. The image is\n# the module's own, in ~/.local/share/feh/wallpapers. feh_set changes the wallpaper for a session\n# without touching this file.\nfeh --no-fehbg --bg-fill \"$HOME/.local/share/feh/wallpapers/default.jpg\"\n"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "wallpapers",
+        "kind": "archive",
+        "from": "wallpaper"
+      },
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/feh-tools",
+        "binary": "feh-tools",
+        "loads": [
+          "feh-tools"
+        ]
+      }
+    ]
+  },
+  "contributions": [
+    {
+      "seat": "node-display-session",
+      "kind": "config",
+      "content": "# The wallpaper's key (module feh, novox/hq ADR 0208). Owned by the mesh: replaced at every push.\n# It puts the declared wallpaper back, after a monitor change or a wallpaper set for the session.\nbindsym $mod+Shift+b exec --no-startup-id ~/.fehbg\n"
+    }
+  ]
+}