Add support for remaining, currently not-supported database objects

[zacateras]

Currently, some database object types are planned in the specs but are not fully implemented in the current SQL scripting engine.

Add support for the remaining currently unsupported object types listed in specs/04-scripting.md:

• Standalone Trigger (excluding table-scoped DML triggers already emitted inline with tables)
• DdlTrigger
• Rule
• Certificate
• SymmetricKey
• AsymmetricKey
• SecurityPolicy
• ExternalDataSource
• ExternalFileFormat
• ExternalTable

Context:

• Current active object types for status / diff / pull are: Table, View, StoredProcedure, Function, Sequence, Schema, Role, User, Synonym, UserDefinedType, PartitionFunction, and PartitionScheme.
• Update 2026.04.08 - implemented with Enhance SyncCommandService and Tests for New SQL Object Types #37: TableType, XmlSchemaCollection, FullTextCatalog, FullTextStoplist, SearchPropertyList, MessageType, Contract, Queue, Service, Route, EventNotification, ServiceBinding
• The scripting spec says planned types must eventually define deterministic discovery, deterministic output shape, and baseline folder mapping integration.

Acceptance criteria:

• Implement support for each remaining unsupported object type listed above, or explicitly document any intentional deferrals.
• Ensure deterministic discovery for each supported type.
• Ensure deterministic output/script shape for each supported type.
• Integrate each supported type with schema-folder mapping and status / diff / pull workflows as appropriate.
• Add or update tests and specs for the new coverage.
• Preserve current behavior for already supported object types.

Specs to review first:

• specs/04-scripting.md
• specs/03-schema-folder.md
• specs/09-architecture.md
• specs/12-project-plan.md