Python: Enhance _OutputItemTracker to prevent duplicate function call streaming

[Chinedum Echeta (cecheta)]

Motivation & Context

Fixes bug where function call was duplicated when streaming response from declaration-only tool,

Description & Review Guide

When the agent invokes the declaration-only tool, there is a second function call emitted containing just metadata. Both of these tools were being streamed to the user.

Related Issue

Fixes #7485

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change. If it is a breaking change, add the breaking change label (or add "[BREAKING]" to the title prefix, before or after any language prefix) — a workflow keeps the label and title prefix in sync automatically.

[github-actions]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/foundry_hosting/agent_framework_foundry_hosting
_responses.py	720	94	86%	144–145, 159, 162–163, 213, 228, 290, 349–352, 388–389, 392, 396, 428, 507, 510, 514, 580, 642–643, 999, 1011, 1463–1464, 1468, 1513, 1515, 1517, 1519, 1523, 1531, 1534–1538, 1540, 1550, 1554, 1601–1606, 1610–1611, 1619–1625, 1655–1656, 1658–1659, 1661, 1666, 1674–1675, 1677, 1682–1686, 1688, 1695–1696, 1698–1699, 1705, 1707–1711, 1721, 1727, 1751, 1757, 1763, 1765, 1767–1770, 1778, 1780
TOTAL	45637	4253	90%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
9245	36 💤	0 ❌	0 🔥	2m 34s ⏱️

[Copilot]

Pull request overview

Fixes a Foundry Hosting streaming bug in the Python implementation where a declaration-only tool invocation can result in a duplicate function_call output item being streamed to the client. The change extends the streaming output-item tracker to recognize and suppress the metadata-only duplicate call, and adds a regression test covering the scenario.

Changes:

• Track previously-streamed function call call_ids during a streaming response.
• Suppress streaming of metadata-only duplicate function-call updates for already-seen call_ids.
• Add a regression test ensuring only one function_call output item is emitted for declaration-only metadata follow-ups.

Show a summary per file

File	Description
python/packages/foundry_hosting/agent_framework_foundry_hosting/_responses.py	Adds duplicate-detection logic in _OutputItemTracker to prevent streaming a second metadata-only function call item.
python/packages/foundry_hosting/tests/test_responses.py	Adds a regression test reproducing the declaration-only metadata duplication scenario in streaming mode.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Lite

[Copilot]

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0 new
• Review effort level: Lite