create_instance had an if/else where the else branch handled both compose
and manifest types. For manifest types, compose_template is NULL (migrated
tools no longer store raw compose strings), so render_compose_template(None,...)
crashed with 'NoneType' object has no attribute 'replace'.
Add an explicit elif tool_type.definition_type == 'manifest' branch that:
1. Looks up the ToolDefinitionManifest from tool_type.manifest_id
2. Resolves base definition if referenced
3. Computes deterministic image tag
4. Generates compose via compile_compose
Legacy compose types continue to use render_compose_template in the else branch.
Alex Blank
1e7bd0a540