Python: Support agent thread

[alliscode]

Python support for common agent API

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/agents
agent.py	114	15	87%	43, 50, 54, 63–74, 83, 120, 227–229
semantic_kernel/agents/autogen
autogen_conversable_agent.py	116	12	90%	67, 73, 84–86, 247–248, 257–260, 289
semantic_kernel/agents/azure_ai
azure_ai_agent.py	174	29	83%	76, 84–85, 90–92, 97–106, 157, 159, 165, 176–181, 183, 185, 206–209, 276, 374, 443, 505, 543, 548
azure_ai_channel.py	41	3	93%	93, 120–121
semantic_kernel/agents/bedrock
bedrock_agent.py	247	52	79%	77–83, 92, 158, 290, 309, 325–328, 334, 336, 339, 344, 379, 411–431, 435, 470, 489–492, 494–497, 539, 550–551, 563, 599–610, 621, 638–651, 668–677, 697, 702
bedrock_agent_base.py	141	41	71%	101, 119–120, 145, 158–160, 187, 206–208, 213, 232–234, 239, 243–244, 264–266, 275, 294–298, 303, 322–326, 331, 343–345, 357–376
semantic_kernel/agents/channels
bedrock_agent_channel.py	79	5	94%	178–187, 194, 208–209
chat_history_channel.py	69	2	97%	147, 150
semantic_kernel/agents/chat_completion
chat_completion_agent.py	210	19	91%	76, 82, 94, 99–103, 161, 164, 174, 182–187, 196, 339, 405, 466, 504
semantic_kernel/agents/open_ai
open_ai_assistant_agent.py	239	17	93%	79, 93–95, 100–110, 267, 280, 316, 458, 463, 535, 635, 733
TOTAL	21184	2408	89%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3336	5 💤	0 ❌	0 🔥	1m 38s ⏱️