feat(azure): add SQLDatabaseSchema adapter (#4415)

<!-- CURSOR_AGENT_PR_BODY_BEGIN -->
## Summary

Create Azure adapter for SQL Database Schemas (child resource of SQL
Server → SQL Database).

## Changes

- **Client interface**
(`sources/azure/clients/sql-database-schemas-client.go`): Wraps Azure
SDK `DatabaseSchemasClient` with `Get` and `ListByDatabase` methods
- **Adapter implementation**
(`sources/azure/manual/sql-database-schema.go`): SearchableWrapper with
3-level composite key (serverName, databaseName, schemaName)
- **Registration** (`sources/azure/manual/adapters.go`): Register
adapter in both active and placeholder blocks
- **Unit tests** (`sources/azure/manual/sql-database-schema_test.go`):
Comprehensive test coverage including edge cases
- **Integration test**
(`sources/azure/integration-tests/sql-database-schema_test.go`): Tests
against live Azure APIs

## Architecture

- **Parent chain**: SQL Server → SQL Database → Database Schema
- **Wrapper type**: SearchableWrapper (deeply nested, 3 path params
after resourceGroup)
- **`Get`** requires: serverName, databaseName, schemaName
- **`Search`** requires: serverName, databaseName (lists all schemas
under that database)
- **Links back** to parent SQLDatabase resource via composite key

The parent adapter `sql-database.go` already has a SEARCH link to
SQLDatabaseSchema (added in a prior PR).

## Self-Review Checklist

- [x] **IAMPermissions**: Present, references
`Microsoft.Sql/servers/databases/schemas/read`
- [x] **PredefinedRole**: Present, uses `Reader`
- [x] **LinkedItemQueries**: 1 link verified (parent SQLDatabase via
GET)
- [x] **PotentialLinks**: 1 type listed (SQLDatabase), matches
LinkedItemQueries
- [x] **Unit tests**: All passing (Get, Search, SearchStream,
StaticTests, ErrorHandling, edge cases)
- [x] **Integration test**: All sub-tests passing (Setup, Run, Teardown)
against live Azure APIs

All checklist items passed. Ready for review.

Closes: ENG-3372
<!-- CURSOR_AGENT_PR_BODY_END -->

Linear Issue:
[ENG-3372](https://linear.app/overmind/issue/ENG-3372/create-azure-adapter-sqldatabaseschema)

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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Lionel Wilson <Lionel-Wilson@users.noreply.github.com>
GitOrigin-RevId: a2944706e235d4e386a3c9ba5412ed938d0fce25

Author: 2 people

sources/azure/clients/sql-database-schemas-client.go

@@ -0,0 +1,35 @@
+package clients
+
+import (
+	"context"
+
+	"github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/sql/armsql/v2"
+)
+
+//go:generate mockgen -destination=../shared/mocks/mock_sql_database_schemas_client.go -package=mocks -source=sql-database-schemas-client.go
+
+// SqlDatabaseSchemasPager is a type alias for the generic Pager interface with database schema response type.
+type SqlDatabaseSchemasPager = Pager[armsql.DatabaseSchemasClientListByDatabaseResponse]
+
+// SqlDatabaseSchemasClient is an interface for interacting with Azure SQL database schemas
+type SqlDatabaseSchemasClient interface {
+	Get(ctx context.Context, resourceGroupName, serverName, databaseName, schemaName string) (armsql.DatabaseSchemasClientGetResponse, error)
+	ListByDatabase(ctx context.Context, resourceGroupName, serverName, databaseName string) SqlDatabaseSchemasPager
+}
+
+type sqlDatabaseSchemasClient struct {
+	client *armsql.DatabaseSchemasClient
+}
+
+func (c *sqlDatabaseSchemasClient) Get(ctx context.Context, resourceGroupName, serverName, databaseName, schemaName string) (armsql.DatabaseSchemasClientGetResponse, error) {
+	return c.client.Get(ctx, resourceGroupName, serverName, databaseName, schemaName, nil)
+}
+
+func (c *sqlDatabaseSchemasClient) ListByDatabase(ctx context.Context, resourceGroupName, serverName, databaseName string) SqlDatabaseSchemasPager {
+	return c.client.NewListByDatabasePager(resourceGroupName, serverName, databaseName, nil)
+}
+
+// NewSqlDatabaseSchemasClient creates a new SqlDatabaseSchemasClient from the Azure SDK client
+func NewSqlDatabaseSchemasClient(client *armsql.DatabaseSchemasClient) SqlDatabaseSchemasClient {
+	return &sqlDatabaseSchemasClient{client: client}
+}