fix: Make experimental Agent compatible with Haystack main and Haystack 2.19

[sjrl]

Related Issues

• fixes failing test for tutorial https://github.com/deepset-ai/haystack-tutorials/actions/runs/18968436340/job/54170222679?pr=414

Proposed Changes:

• Make experimental Agent compatible with Haystack main and Haystack 2.19. Once Haystack 2.20 is out we can drop the if-check but I thought in the off chance we release a new version of haystack-experimental before we release Haystack 2.20 it would be best to still make sure this works with Haystack 2.19
• Issue arose from this PR feat: Auto call warm up on components that take in ChatGenerators as input haystack#9987

How did you test it?

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 18968856152

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 77 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 71.003%

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Files with Coverage Reduction	New Missed Lines	%
components/agents/agent.py	77	34.91%

Totals
Change from base Build 18958659706:	-0.2%
Covered Lines:	1119
Relevant Lines:	1576

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💛 - Coveralls

[anakin87]

👍