Add test artifacts quick reference documentation

Add quick reference guide for multi-attachment test artifacts including
installation instructions and resource summary.

- Add MULTI_TEST_ARTIFACTS_README.md with quick start guide
- Document all test policies and thing groups
- Include installation/uninstallation instructions

Author: rpcme

configs/MULTI_TEST_ARTIFACTS_README.md

@@ -0,0 +1,71 @@
+# Multi-Attachment Test Artifacts - Quick Reference
+
+## Files
+
+**Policies (3):**
+- `multi-test-policy-base.json` - Base connectivity
+- `multi-test-policy-sensor.json` - Sensor telemetry
+- `multi-test-policy-admin.json` - Admin operations
+
+**Thing Groups (3):**
+- `multi-test-thing-group-dept.json` - Department: Engineering
+- `multi-test-thing-group-location.json` - Location: Seattle
+- `multi-test-thing-group-product.json` - Product: Sensor
+
+**Scripts:**
+- `../scripts/install-multi-test-artifacts.sh` - Install all resources
+- `../scripts/uninstall-multi-test-artifacts.sh` - Remove all resources
+
+**Documentation:**
+- `multi-attachment-test-artifacts.md` - Full specification
+
+## Quick Start
+
+### Install Resources
+
+```bash
+cd /path/to/thingpress
+./scripts/install-multi-test-artifacts.sh us-east-1
+```
+
+### Uninstall Resources
+
+```bash
+./scripts/uninstall-multi-test-artifacts.sh us-east-1
+```
+
+## Resources Created
+
+| Type | Name | Purpose |
+|------|------|---------|
+| Policy | MultiTestBasePolicy | Base connectivity |
+| Policy | MultiTestSensorPolicy | Sensor operations |
+| Policy | MultiTestAdminPolicy | Admin operations |
+| Thing Group | multi-test-dept-engineering | Department hierarchy |
+| Thing Group | multi-test-location-seattle | Location hierarchy |
+| Thing Group | multi-test-product-sensor | Product hierarchy |
+
+## Test Configuration
+
+Use in SAM config:
+
+```toml
+parameter_overrides = "IoTPolicies=\"MultiTestBasePolicy,MultiTestSensorPolicy,MultiTestAdminPolicy\" IoTThingGroups=\"multi-test-dept-engineering,multi-test-location-seattle,multi-test-product-sensor\" ..."
+```
+
+## Cleanup
+
+The uninstall script handles cleanup, but if manual cleanup is needed:
+
+```bash
+# Detach policies from certificates first
+aws iot list-targets-for-policy --policy-name MultiTestBasePolicy
+# Then detach each...
+
+# Remove things from groups first
+aws iot list-things-in-thing-group --thing-group-name multi-test-dept-engineering
+# Then remove each...
+
+# Then run uninstall script
+./scripts/uninstall-multi-test-artifacts.sh
+```