hl exec-rules: the model looks at what it may run; Nextcloud's receipt checks are on the allowlist

The first post-upgrade check on Nextcloud could run nothing: every hl exec, even `id`, was refused by the allowlist (only the
three db:add-* commands were on it, and the model had no way to know). `hl exec-rules` (route /agent/exec-rules) lists the
exact commands the session's project accepts, and the repair and post-upgrade prompts send the model there first. The
allowlist gets the read-only receipt check of the skill: occ status (with and without --output=json), occ config:app:get core
lastcron, occ app:list and pidof crond in the cron service. A test holds the file to this exact list. No new dependency.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

config/agent-exec.json

@@ -1,4 +1,56 @@
 [
+  {
+    "project": "nextcloud",
+    "service": "app",
+    "user": "www-data",
+    "argv": [
+      "php",
+      "occ",
+      "status"
+    ]
+  },
+  {
+    "project": "nextcloud",
+    "service": "app",
+    "user": "www-data",
+    "argv": [
+      "php",
+      "occ",
+      "status",
+      "--output=json"
+    ]
+  },
+  {
+    "project": "nextcloud",
+    "service": "app",
+    "user": "www-data",
+    "argv": [
+      "php",
+      "occ",
+      "config:app:get",
+      "core",
+      "lastcron"
+    ]
+  },
+  {
+    "project": "nextcloud",
+    "service": "app",
+    "user": "www-data",
+    "argv": [
+      "php",
+      "occ",
+      "app:list"
+    ]
+  },
+  {
+    "project": "nextcloud",
+    "service": "cron",
+    "user": null,
+    "argv": [
+      "pidof",
+      "crond"
+    ]
+  },
   {
     "project": "nextcloud",
     "service": "app",