docs(P27): update docs + README for RDS primitive + module examples

- docs/modules/index.md: add rds primitive row + Examples section
- docs/consumer-guide.md: reference examples/ directory + microservice sample
- docs/contracts/index.md: reference both sample contracts + module examples
- README.md: add rds to primitives list, note examples/ dirs, update contracts row

---ci---
project: acdl
phase: 27
milestone: v1.7
status: execute
---/ci---

docs/modules/index.md

@@ -25,6 +25,7 @@ module's README documents which resources it creates.
 | `ecr` | `aws_ecr_repository` — ECR container image repository | [modules/l1/ecr/README.md](https://github.com/acdl/acdl/blob/main/modules/l1/ecr/README.md) |
 | `cloudfront` | `aws_cloudfront_distribution` + `aws_cloudfront_origin_access_control` — CloudFront distribution with S3 origin via OAC | [modules/l1/cloudfront/README.md](https://github.com/acdl/acdl/blob/main/modules/l1/cloudfront/README.md) |
 | `waf` | `aws_wafv2_web_acl` — WAFv2 Web ACL (CloudFront-scoped) | [modules/l1/waf/README.md](https://github.com/acdl/acdl/blob/main/modules/l1/waf/README.md) |
+| `rds` | `aws_db_instance` — RDS database instance (multi-engine: postgres, mysql, etc.) | [modules/l1/rds/README.md](https://github.com/acdl/acdl/blob/main/modules/l1/rds/README.md) |
 
 ## Modules
 
@@ -39,6 +40,14 @@ Module versions are tracked in
 [`registry.json`](https://github.com/acdl/acdl/blob/main/modules/registry.json).
 Both primitives and modules are registered.
 
+## Examples
+
+Each module has a `examples/` directory containing validated consumer
+contract examples (`simple.yaml` + `complex.yaml` + variation files). The
+platform-test pipeline validates them against
+[`schemas/contract.schema.json`](https://github.com/acdl/acdl/blob/main/schemas/contract.schema.json).
+See each module's `## Examples` section for the excerpts.
+
 ## Versioning
 
 Primitives and modules use semver: interface → MAJOR, behavior → MINOR,