fix: tool_call simulation in agent messages

[priyansh4320]

Why are these changes needed?

This PR fixes model tool call simulation for Ollama model client

Related issue number

#2283

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/latest/docs/contributor-guide/documentation/ to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[joggrbot]

📝 Documentation Analysis

All docs are up to date! 🎉

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✅ Latest commit analyzed: 961dda7 | Powered by Joggr

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
autogen/oai/ollama.py	0.00%	4 Missing ⚠️

Files with missing lines	Coverage Δ
autogen/oai/ollama.py	19.47% <0.00%> (-0.67%)	⬇️

... and 19 files with indirect coverage changes

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