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/mcp/nav.json

@@ -69,6 +69,11 @@
     "resource": "docs://modules/auth_integration",
     "title": "Auth Integration"
   },
+  {
+    "module": "repository_inventory",
+    "resource": "docs://modules/repository_inventory",
+    "title": "Repository Inventory"
+  },
   {
     "module": "index",
     "resource": "docs://modules/index",