Publish the policy-nexus arc42 stub

Inventory now discovers docs/architecture and registers the local
first-wave stub at /architecture/policy-nexus/v0.1/.

docs/adr-review/SUMMARY.md

@@ -1,18 +1,18 @@
 # ADR review ledger summary
 
-Rows: 125
+Rows: 126
 
 ## Inventory dispositions
 
 - `excluded`: 2
 - `metadata-pending`: 105
-- `published`: 10
+- `published`: 11
 - `unsupported-format`: 8
 
 ## Proposed dispositions
 
 - `publish`: 9
-- `unreviewed`: 116
+- `unreviewed`: 117
 
 ## Front-matter `id` collisions
 

docs/adr-review/ledger.json

@@ -2240,6 +2240,33 @@
       "source_repo": "policy-nexus",
       "successor": ""
     },
+    {
+      "bare_adr": "",
+      "bare_adr_collisions": [],
+      "conflict_kinds": [],
+      "file_present": true,
+      "frontmatter": {
+        "id": "policy-nexus-architecture",
+        "last_reviewed": "2026-08-18",
+        "owner": "the-custodian",
+        "review_interval": "6m",
+        "revision": "draft-1",
+        "status": "proposed",
+        "title": "Policy Nexus architecture",
+        "updated": "",
+        "version": "0.1"
+      },
+      "id_collisions": [],
+      "inventory_disposition": "published",
+      "inventory_reason": "Published through an explicit publication.json document entry.",
+      "missing_fields": [],
+      "notes": "",
+      "proposed_disposition": "unreviewed",
+      "review_notes": "",
+      "source_path": "docs/architecture/policy-nexus_v0.1.md",
+      "source_repo": "policy-nexus",
+      "successor": ""
+    },
     {
       "bare_adr": "ADR-0002",
       "bare_adr_collisions": [