docs: describe the tool call limits of the AI providers

[tomivirkki]

Summary

• Documents the per-turn tool call limits introduced in feat: cap tool calls per turn in LangChain4JLLMProvider flow-components#10138, so readers know why a turn that keeps calling tools fails and how to tune the bounds
• Describes how the failure surfaces as a ToolCallLimitExceededException in the response listener, in line with the provider alignment in fix: fail the turn when Spring AI stops at its tool call limit flow-components#10144
• Points Spring AI users to Spring AI's own configuration, since the provider adds no limit of its own

Depends on vaadin/flow-components#10144 being merged and cherry-picked to 25.3.

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Changed pages

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• flow/ai-support/listeners — modified, +1/-1 lines, 1 removal marker(s)
• flow/ai-support/llm-providers — modified, +40/-0 lines
• flow/ai-support/tool-calling — modified, +4/-0 lines

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