.NET: Python: Add AGENTS.md files and update coding standards (#3644)

* Add AGENTS.md files and update coding standards for Python

- Add root python/AGENTS.md with project structure and package links
- Add AGENTS.md for each package describing purpose and main classes
- Update .github/copilot-instructions.md with improved structure
- Update python/CODING_STANDARD.md with API review guidance:
  - Future annotations convention (#3578)
  - TypeVar naming convention (#3594)
  - Mapping vs MutableMapping (#3577)
  - Avoid shadowing built-ins (#3583)
  - Explicit exports (#3605)
  - Exception documentation guidelines (#3410)
- Simplify python/.github/instructions/python.instructions.md to reference AGENTS.md
- Remove AGENTS.md from .gitignore

* Fix purview import path in AGENTS.md

* Address PR review comments and restructure instructions

- Slim down .github/copilot-instructions.md to reference language-specific docs
- Add ADR section explaining templates and purpose
- Create dotnet/AGENTS.md with .NET-specific build commands, conventions, and sample guidance
- Update Python build/test instructions for core vs isolated changes
- Fix Microsoft.Extensions.AI package references
- Update kwargs guidance per issue #3642
- Fix Python sample helper placement (top, not bottom)
- Document new 'typing' poe task in DEV_SETUP.md

* Add 'typing' poe task to run both pyright and mypy

* Add kwargs guidelines from issue #3642 to CODING_STANDARD.md

* Clarify that connector packages pull in core as dependency

python/packages/declarative/AGENTS.md

@@ -0,0 +1,33 @@
+# 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
+- **`DeclarativeLoaderError`** / **`ProviderLookupError`** - 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
+
+agent = AgentFactory.create_from_file("agent.yaml")
+workflow = WorkflowFactory.create_from_file("workflow.yaml")
+```
+
+## Import Path
+
+```python
+from agent_framework.declarative import AgentFactory, WorkflowFactory
+# or directly:
+from agent_framework_declarative import AgentFactory
+```