[BREAKING] Python: Move orchestrations to dedicated package (#3685)

* Move orchestrations to dedicated package

* Merge main

* Fix markdown links

* Fix links

python/packages/orchestrations/README.md

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+# Agent Framework Orchestrations
+
+Orchestration patterns for Microsoft Agent Framework. This package provides high-level builders for common multi-agent workflow patterns.
+
+## Installation
+
+```bash
+pip install agent-framework-orchestrations
+```
+
+## Orchestration Patterns
+
+### SequentialBuilder
+
+Chain agents/executors in sequence, passing conversation context along:
+
+```python
+from agent_framework_orchestrations import SequentialBuilder
+
+workflow = SequentialBuilder().participants([agent1, agent2, agent3]).build()
+```
+
+### ConcurrentBuilder
+
+Fan-out to multiple agents in parallel, then aggregate results:
+
+```python
+from agent_framework_orchestrations import ConcurrentBuilder
+
+workflow = ConcurrentBuilder().participants([agent1, agent2, agent3]).build()
+```
+
+### HandoffBuilder
+
+Decentralized agent routing where agents decide handoff targets:
+
+```python
+from agent_framework_orchestrations import HandoffBuilder
+
+workflow = (
+    HandoffBuilder()
+    .participants([triage, billing, support])
+    .with_start_agent(triage)
+    .build()
+)
+```
+
+### GroupChatBuilder
+
+Orchestrator-directed multi-agent conversations:
+
+```python
+from agent_framework_orchestrations import GroupChatBuilder
+
+workflow = (
+    GroupChatBuilder()
+    .with_orchestrator(selection_func=my_selector)
+    .participants([agent1, agent2])
+    .build()
+)
+```
+
+### MagenticBuilder
+
+Sophisticated multi-agent orchestration using the Magentic One pattern:
+
+```python
+from agent_framework_orchestrations import MagenticBuilder
+
+workflow = (
+    MagenticBuilder()
+    .participants([researcher, writer, reviewer])
+    .with_manager(agent=manager_agent)
+    .build()
+)
+```
+
+## Usage with agent_framework
+
+You can also import orchestrations through the main agent_framework package:
+
+```python
+from agent_framework.orchestrations import SequentialBuilder, ConcurrentBuilder
+```
+
+## Documentation
+
+For more information, see the [Agent Framework documentation](https://aka.ms/agent-framework).