Python: Add declarative workflow runtime

[moonbox3]

Motivation and Context

Adds a graph-based runtime for executing declarative YAML workflows, enabling multi-agent orchestration without writing Python code.

Features

• Workflow Graph Builder: Transforms YAML workflow definitions into executable directed graphs
• Action Executors: SetValue, SendActivity, Foreach, If/Switch, RepeatUntil, GotoAction, InvokeAzureAgent, and more
• Expression Evaluation: PowerFx-style expressions with namespace support (Local., System., Workflow.)
• Human-in-the-Loop: Question, WaitForInput, and RequestExternalInput actions for interactive workflows
• Schema Validation: Required field checking, duplicate ID detection, and self-referencing goto detection

Samples

• simple_workflow: Basic variables, conditionals, and loops
• conditional_workflow: Nested branching based on user input
• human_in_loop: Interactive workflows requesting user input
• function_tools: Invoking Python functions from workflows
• customer_support, marketing, deep_research, student_teacher: Multi-agent patterns

Description

• Closes Python runtime for Declarative Workflows (Epic) #2727

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/_workflows
_edge.py	227	28	87%	41, 63–64, 66, 161, 191, 442–443, 448, 452–457, 459–461, 577, 691, 698–700, 747, 775, 801, 855, 869
_edge_runner.py	162	13	91%	53, 58, 71, 138–139, 143, 150, 206, 211, 355–356, 360, 401
_group_chat.py	605	107	82%	114, 150, 161, 385–395, 414, 441–442, 447, 509, 523, 530, 534–536, 539, 591–592, 594–596, 620–621, 677–686, 695–696, 699, 744, 758–760, 764, 766–770, 775, 777, 783, 787–789, 794–799, 805, 820, 843, 852, 875, 884, 889–890, 1052, 1071, 1075, 1129, 1179, 1197, 1205, 1230–1232, 1471, 1477, 1636, 1650, 1717–1718, 1720–1721, 1723, 1725, 1727–1728, 1964, 2036–2039, 2049, 2060, 2069–2071
_workflow_builder.py	278	36	87%	260, 595, 694, 701–702, 803, 806, 811, 813, 820, 823–827, 829, 891, 966, 969, 1029–1030, 1175, 1189–1196, 1198, 1201, 1203–1205, 1213
packages/core/agent_framework/openai
_chat_client.py	246	48	80%	115–116, 120, 140, 150–151, 153, 164, 180, 190, 195, 201–203, 210, 239, 259, 278, 292, 297–311, 318–320, 395, 401, 405, 408, 410, 412, 421, 435–436, 442, 458
TOTAL	17057	2680	84%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
2948	154 💤	0 ❌	0 🔥	1m 2s ⏱️

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[TaoChenOSU]

These are the comments so far. I will finish the review later today, or tomorrow if I can't get to all of it.

[moonbox3]

@victordibia I had to do some changes here to get declarative workflows to parse properly... can you have a look please? Not sure how it'll jive with your current DevUI PR you have open. Thanks.

[moonbox3]

@eavanvalkenburg @TaoChenOSU did a lot of clean up here. Thanks for the thorough reviews. Please have a look again.

[eavanvalkenburg]

couple of comments, and would also be useful to have a sample showing the workflow in the code itself.