chore: add project documentation framework

.project-docs/20-architecture/system-overview.md

@@ -0,0 +1,22 @@
+# System Overview
+
+## Current Architecture
+
+{short description of the current system shape}
+
+## Main Components
+
+| Component | Responsibility | Notes |
+|---|---|---|
+
+## Important Boundaries
+
+- {boundary that future work should respect}
+
+## Related Decisions
+
+- {ADR reference}
+
+## Last Updated
+
+{YYYY-MM-DD}