chore: import upstream snapshot with attribution

python/packages/declarative/AGENTS.md

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+# Declarative Package (agent-framework-declarative)
+
+YAML/JSON-based declarative agent and workflow definitions.
+
+## Main Classes
+
+- **`AgentFactory`** - Creates agents from declarative definitions
+- **`WorkflowFactory`** - Creates workflows from declarative definitions
+- **`WorkflowState`** - State management for declarative workflows
+- **`ProviderTypeMapping`** - Maps provider types to implementations
+- **`HttpRequestHandler`** / **`DefaultHttpRequestHandler`** - Pluggable HTTP transport for the `HttpRequestAction` declarative action (configured via `WorkflowFactory(http_request_handler=...)`)
+- **`MCPToolHandler`** / **`DefaultMCPToolHandler`** - Pluggable MCP transport for the `InvokeMcpTool` declarative action (configured via `WorkflowFactory(mcp_tool_handler=...)`)
+- **`DeclarativeLoaderError`** / **`ProviderLookupError`** / **`DeclarativeWorkflowError`** / **`DeclarativeActionError`** - Error types
+
+## External Input Handling
+
+- **`ExternalInputRequest`** / **`ExternalInputResponse`** - Human-in-the-loop support
+- **`AgentExternalInputRequest`** / **`AgentExternalInputResponse`** - Agent-level input requests
+
+## Usage
+
+```python
+from agent_framework.declarative import AgentFactory, WorkflowFactory
+
+# Create agent from YAML file
+agent_factory = AgentFactory()
+agent = agent_factory.create_agent_from_yaml_path("agent.yaml")
+
+# Create workflow from YAML file
+workflow_factory = WorkflowFactory()
+workflow = workflow_factory.create_workflow_from_yaml_path("workflow.yaml")
+```
+
+## Import Path
+
+```python
+from agent_framework.declarative import AgentFactory, WorkflowFactory
+# or directly:
+from agent_framework_declarative import AgentFactory
+```