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/src/mkdocs.lib.yml

@@ -65,6 +65,7 @@ nav:
   - Infra Adapters: 09_infra_adaptors.md
   - Drone Pipelines: 10_drone_pipelines.md
   - Versioning & Changelog: 11_versioning_and_changelog.md
+  - Repository Inventory: 15_repository_inventory.md
   - Genericity Matrix: 12_genericity_matrix.md
   - Auth Integration: 14_auth_integration.md
   - Library Registry: 13_library_registry.md