feat(databases-on-aws): migrate aurora-dsql to databases-on-aws plugin

Renames aurora-dsql plugin to databases-on-aws as the top-level plugin
for the AWS database portfolio. Migrates the DSQL skill into
skills/dsql/ within the new plugin structure.

Key changes:
- Rename plugin from aurora-dsql to databases-on-aws
- Split oversized reference files per Agent Skills spec (<100 lines)
  into subdirectories: auth/, examples/, platforms/, tools/
- Add AWS Knowledge MCP (awsknowledge) for verifying numeric limits
  with inline delegation hints in authoritative reference files
- Add explicit Table Recreation Pattern warning for unsupported DDL
  (ALTER COLUMN TYPE, DROP COLUMN, DROP CONSTRAINT)
- Add automated eval harness (triggering + functional with assertions)
- Update marketplace.json, CODEOWNERS, and .mcp.json

Co-authored-by: anwesham-lab <64298192+anwesham-lab@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: anwesham-lab

.claude-plugin/marketplace.json

@@ -118,32 +118,27 @@
     },
     {
       "category": "database",
-      "description": "Build with Aurora DSQL - manage schemas, execute queries, handle migrations, and develop applications with a serverless, distributed SQL database with PostgreSQL compatibility.",
+      "description": "Expert database guidance for the AWS database portfolio. Design schemas, execute queries, handle migrations, and choose the right database for your workload.",
       "keywords": [
         "aws",
         "aws agent skills",
         "amazon",
         "aurora",
-        "dsql",
-        "aurora-dsql",
         "database",
+        "databases",
         "distributed-sql",
-        "distributed",
-        "distributed-database",
-        "serverless",
-        "serverless-database",
+        "dsql",
+        "iam-auth",
+        "migration",
         "postgresql",
         "postgres",
-        "sql",
         "schema",
-        "migration",
-        "multi-tenant",
-        "iam-auth",
-        "mcp"
+        "serverless",
+        "sql"
       ],
-      "name": "aurora-dsql",
-      "source": "./plugins/aurora-dsql",
-      "tags": ["aws", "database", "dsql", "aurora", "distributed-sql", "serverless", "postgresql"],
+      "name": "databases-on-aws",
+      "source": "./plugins/databases-on-aws",
+      "tags": ["aws", "database", "aurora", "dsql", "serverless", "postgresql"],
       "version": "1.0.0"
     }
   ]

.github/CODEOWNERS

@@ -31,7 +31,7 @@ tools/                              @awslabs/agent-plugins-admins
 ## Plugins (alphabetically listed)
 
 plugins/amazon-location-service     @awslabs/agent-plugins-admins @awslabs/agent-plugins-maintainers  @awslabs/agent-plugins-amazon-location-service
-plugins/aurora-dsql                 @awslabs/agent-plugins-admins @awslabs/agent-plugins-maintainers  @awslabs/agent-plugins-dsql
+plugins/databases-on-aws            @awslabs/agent-plugins-admins @awslabs/agent-plugins-maintainers  @awslabs/agent-plugins-dsql
 plugins/aws-amplify                 @awslabs/agent-plugins-admins @awslabs/agent-plugins-maintainers  @awslabs/agent-plugins-amplify
 plugins/aws-serverless              @awslabs/agent-plugins-admins @awslabs/agent-plugins-maintainers  @awslabs/agent-plugins-aws-serverless
 plugins/deploy-on-aws               @awslabs/agent-plugins-admins @awslabs/agent-plugins-maintainers  @awslabs/agent-plugins-deploy-on-aws