docs: establish project documentation baseline

Provide installation, security, contribution, licensing, and release guidance while removing user-specific service configuration.

docs/README.md

@@ -0,0 +1,22 @@
+# Documentation index
+
+## Reason for existence
+
+Point contributors and operators to the authoritative document for each concern without duplicating implementation detail.
+
+| Need | Authoritative document |
+| --- | --- |
+| Install, run, and verify the project | [`../README.md`](../README.md) |
+| Understand boundaries and security invariants | [`../DESIGN.md`](../DESIGN.md) |
+| Follow implementation milestones | [`../IMPLEMENTATION_PLAN.md`](../IMPLEMENTATION_PLAN.md) |
+| Execute acceptance and soak testing | [`../TEST_PLAN.md`](../TEST_PLAN.md) |
+| Understand the desktop product surface | [`../specs/FULL_PI_PANEL_SPEC.md`](../specs/FULL_PI_PANEL_SPEC.md) |
+| Understand Tauri integration | [`../specs/TAURI_CLIENT_ARCHITECTURE.md`](../specs/TAURI_CLIENT_ARCHITECTURE.md) |
+| Contribute safely | [`../CONTRIBUTING.md`](../CONTRIBUTING.md) |
+| Report vulnerabilities | [`../SECURITY.md`](../SECURITY.md) |
+
+## Verification
+
+```bash
+test -f README.md && test -f DESIGN.md && test -f TEST_PLAN.md
+```