feat: add Laya integration

[sjrl]

Related Issues

• Related to Laya integration #4024

Proposed Changes:

Adds laya-haystack with LayaDocumentClassifier, which uses the open-weight Laya decision model to answer typed questions (choice, score, noul) about each document in a single batched forward pass. The calibrated answers are stored in meta["laya"], keyed by question ID. The model loads on the first run().

How did you test it?

Unit tests, plus an integration test that runs the real model. Integration tests run in CI on Linux with Python 3.10 only, since each run downloads the model.

Notes for the reviewer

The docs-website page will follow in a separate PR.

After discussion with @julian-risch and @ju-gu offline we thought it would be a good idea to create an integration for these new types of decision models since Sol is actively using them for clients already. Depending on how the popularity of these models progress over time we can decide to archive this integration.

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:.

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	pypi/​laya@​0.3.21

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Coverage report (laya)

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
integrations/laya/src/haystack_integrations/components/classifiers/laya
document_classifier.py
integrations/laya/src/haystack_integrations/components/routers/laya
text_router.py
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