feat(standards): MR-based tag strategy + repository inventory (registry://repos)

Versioning standard now documents the MR flow: bump pyproject.toml/VERSION and promote CHANGELOG in the MR (referencing the version/tag, not a commit id), merge/squash, then tag the resulting commit. Adds the agent-assisted tagging procedure (wait for the go-ahead, find the version-bump commit, tag only it, ask the user to push) to both the reference page and the releasing wiki runbook. Adds the repo inventory (src/repos.json -> mcp/repos.json), the registry://repos resource + list_repos tool, the 15_repository_inventory lib page, and two MCP prompts: compliance (remediate repos) and release (agent tagging).

standards/lib/02_layering_rules/index.html

@@ -584,6 +584,28 @@
   
   
   
+    <li class="md-nav__item">
+      <a href="../15_repository_inventory/" class="md-nav__link">
+        
+  
+  
+  <span class="md-ellipsis">
+    Repository Inventory
+    
+  </span>
+  
+
+      </a>
+    </li>
+  
+
+    
+      
+      
+  
+  
+  
+  
     <li class="md-nav__item">
       <a href="../12_genericity_matrix/" class="md-nav__link">