updated recommended model list for agent builder

[abhi-elastic]

closes https://github.com/elastic/search-team/issues/12519
closes https://github.com/elastic/docs-content-internal/issues/649

Summary

This pull request updates the documentation for model selection in the agent-builder guide, providing clearer guidance on choosing models based on reasoning capability, throughput, and use case.
The changes introduce:

• A categorized table of model recommendations, and outline trade-offs
• A tip about choosing models with apt context window based on workflow.

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

[github-actions]

Vale Linting Results

Summary: 1 suggestion found

💡 Suggestions (1)

File	Line	Rule	Message
explore-analyze/ai-features/agent-builder/limitations-known-issues.md	43	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.

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[github-actions]

🔍 Preview links for changed docs

• explore-analyze/ai-features/agent-builder/limitations-known-issues.md
• explore-analyze/ai-features/agent-builder/models.md

[leemthompo]

LGTM writing wise, with some teeny nits. Thanks @abhi-elastic!

Writers can follow up by moving existing related content in the known issues in here to preface the "incompatible models" list