docs: add TOPOLOGY.md

Author: hyperpolymath

TOPOLOGY.md

@@ -0,0 +1,29 @@
+<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk> -->
+# TOPOLOGY.md — k9-validate-action
+
+## Purpose
+
+GitHub Action that validates `.k9` and `.k9.ncl` contractile files in a repository. Enforces K9! magic number, required field presence, security-tier constraints, and leash model compliance. Used in CI pipelines across RSR repos.
+
+## Module Map
+
+```
+k9-validate-action/
+├── action.yml            # GitHub Action metadata and entry point
+├── src/
+│   └── validate-k9.sh    # Validation script
+├── examples/             # Example workflows using this action
+├── docs/                 # Usage documentation
+└── container/            # Containerfile for CI
+```
+
+## Data Flow
+
+```
+[GitHub workflow trigger] ──► [action.yml] ──► [validate-k9.sh]
+                                                      │
+                                          [scan repo for .k9 / .k9.ncl]
+                                                      │
+                                             [pass / fail with annotations]
+```