Python: restructure: Python samples into progressive 01-05 layout (#3862)

* restructure: Python samples into progressive 01-05 layout

- 01-get-started/: 6 numbered steps (hello agent → hosting)
- 02-agents/: all agent concept samples (tools, middleware, providers, etc.)
- 03-workflows/: ALL existing workflow samples preserved as-is
- 04-hosting/: azure-functions, durabletask, a2a
- 05-end-to-end/: demos, evaluation, hosted agents
- Old files moved to _to_delete/ for review
- Added AGENTS.md with structure documentation
- autogen-migration/ and semantic-kernel-migration/ preserved at root

* fix: switch to AzureOpenAI Foundry, fix CI failures

- Switch all 01-get-started samples to AzureOpenAIResponsesClient with
  Azure AI Foundry project endpoint (AZURE_AI_PROJECT_ENDPOINT +
  AZURE_OPENAI_RESPONSES_DEPLOYMENT_NAME + AzureCliCredential)
- Add _to_delete/ and 05-end-to-end/ to pyrightconfig.samples.json excludes
- Fix test paths in packages/ that referenced old getting_started/ dirs:
  durabletask conftest + streaming test, azurefunctions conftest,
  devui conftest + capture_messages + openai_sdk_integration
- Fix workflow_as_agent_human_in_the_loop.py import (sibling import)
- Update hosting READMEs and tool comment paths
- Replace root README.md with new structure overview
- Update AGENTS.md to document Azure OpenAI Foundry as default provider

* cleanup: remove _to_delete folder, copy resource files to active dirs

All files in _to_delete/ were either:
- Exact duplicates of files in the new structure (240 files)
- Same file with only comment path updates (100 files)
- One import-fix diff (workflow_as_agent_human_in_the_loop.py)
- One superseded minimal_sample.py

Resource files (sample.pdf, countries.json, employees.pdf, weather.json)
copied to 02-agents/sample_assets/ and 02-agents/resources/ since active
samples reference them.

* fix: address PR review comments, centralize resources, remove root duplicates

- Fix type annotation in 04_memory.py (string union -> proper types)
- Fix old sample paths in observability files
- Fix grammar/spelling in observability samples
- Move sample_assets/ and resources/ to shared/ folder
- Remove 8 duplicate observability files from 02-agents root
- Update resource path references in multimodal_input and provider samples

* fix: update broken links from old getting_started paths to new structure

- Update relative paths in READMEs: getting_started/ → 01-get-started/,
  02-agents/, 03-workflows/, 04-hosting/, 05-end-to-end/
- Fix absolute GitHub URLs in package READMEs
- Fix broken link in ollama package README

* fix: convert absolute GitHub URLs to relative paths for link checker

Absolute URLs to python/samples/ on main branch 404 until PR merges.
Converted to relative paths that linkspector can verify locally.

* fix: update link for handoff sample moved to orchestrations/

* fix: update chatkit-integration README path from demos/ to 05-end-to-end/

* fix: update broken links in orchestrations README to match flat directory structure

python/samples/03-workflows/declarative/simple_workflow/README.md

@@ -0,0 +1,24 @@
+# Simple Workflow Sample
+
+This sample demonstrates the basics of declarative workflows:
+- Setting variables
+- Evaluating expressions
+- Sending output to users
+
+## Files
+
+- `workflow.yaml` - The workflow definition
+- `main.py` - Python code to execute the workflow
+
+## Running
+
+```bash
+python main.py
+```
+
+## What It Does
+
+1. Sets a greeting variable
+2. Sets a name from input (or uses default)
+3. Combines them into a message
+4. Sends the message as output

python/samples/03-workflows/declarative/simple_workflow/main.py

@@ -0,0 +1,40 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+"""Simple workflow sample - demonstrates basic variable setting and output."""
+
+import asyncio
+from pathlib import Path
+
+from agent_framework.declarative import WorkflowFactory
+
+
+async def main() -> None:
+    """Run the simple greeting workflow."""
+    # Create a workflow factory
+    factory = WorkflowFactory()
+
+    # Load the workflow from YAML
+    workflow_path = Path(__file__).parent / "workflow.yaml"
+    workflow = factory.create_workflow_from_yaml_path(workflow_path)
+
+    print(f"Loaded workflow: {workflow.name}")
+    print("-" * 40)
+
+    # Run with default name
+    print("\nRunning with default name:")
+    result = await workflow.run({})
+    for output in result.get_outputs():
+        print(f"  Output: {output}")
+
+    # Run with a custom name
+    print("\nRunning with custom name 'Alice':")
+    result = await workflow.run({"name": "Alice"})
+    for output in result.get_outputs():
+        print(f"  Output: {output}")
+
+    print("\n" + "-" * 40)
+    print("Workflow completed!")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

python/samples/03-workflows/declarative/simple_workflow/workflow.yaml

@@ -0,0 +1,38 @@
+name: simple-greeting-workflow
+description: A simple workflow that greets the user
+
+actions:
+  # Set a greeting prefix
+  - kind: SetValue
+    id: set_greeting
+    displayName: Set greeting prefix
+    path: Local.greeting
+    value: Hello
+
+  # Set the user's name from input, or use a default
+  - kind: SetValue
+    id: set_name
+    displayName: Set user name
+    path: Local.name
+    value: =If(IsBlank(inputs.name), "World", inputs.name)
+
+  # Build the full message
+  - kind: SetValue
+    id: build_message
+    displayName: Build greeting message
+    path: Local.message
+    value: =Concat(Local.greeting, ", ", Local.name, "!")
+
+  # Send the greeting to the user
+  - kind: SendActivity
+    id: send_greeting
+    displayName: Send greeting to user
+    activity:
+      text: =Local.message
+
+  # Also store it in outputs
+  - kind: SetValue
+    id: set_output
+    displayName: Store result in outputs
+    path: Workflow.Outputs.greeting
+    value: =Local.message