refactor: Update interfaces to include kwargs to enable backwards compatibility

[mkmeral]

Description

This PR adds **kwargs parameters to all model and tool interfaces to enable backwards compatibility and future extensibility.

Note: This is a breaking change that will require users who have implemented custom tools or model providers to update their code to match the new interface
signatures.

Key Changes:

• Model Interfaces: Added **kwargs to stream() and structured_output() methods across all model providers (Bedrock, LiteLLM, LlamaAPI,
Mistral, Ollama, OpenAI, Writer)
• Tool System: Refactored tool interfaces to use invocation_state: dict[str, Any], **kwargs: Any instead of kwargs: dict[str, Any] for better API clarity
• Event Loop: Updated event loop functions to use invocation_state parameter naming for consistency
• Hook System: Updated tool invocation events (BeforeToolInvocationEvent, AfterToolInvocationEvent) to use invocation_state instead of kwargs
• Telemetry/Tracing: Updated tracer methods to use invocation_state parameter naming throughout the tracing system
• Documentation: Added parameter descriptions for all new **kwargs parameters

The refactoring improves API clarity by separating invocation context (invocation_state) from extensibility parameters (**kwargs), while enabling future extensibility without breaking changes.

Breaking Changes:

• Custom tool implementations must update their stream() method signature from stream(self, tool_use: ToolUse, kwargs: dict[str, Any]) to
stream(self, tool_use: ToolUse, invocation_state: dict[str, Any], **kwargs: Any)
• Custom model providers must add **kwargs: Any to their stream() and structured_output() method signatures
• Hook handlers using tool invocation events must update references from kwargs to invocation_state

Related Issues

Documentation PR

Type of Change

Breaking change

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-
docs, agents-tools, agents-cli

• [ x ] I ran hatch run prepare

Testing Coverage:
• All existing tests updated to reflect new parameter naming
• Test coverage maintained across all affected components
• Model provider tests verify **kwargs acceptance
• Tool system tests verify invocation_state and **kwargs handling
• Hook system tests updated for new event parameter structure
• Tracing/telemetry tests updated for invocation_state usage

Checklist

• [ x ] I have read the CONTRIBUTING document
• [ x ] I have added any necessary tests that prove my fix is effective or my feature works
• [ x ] I have updated the documentation accordingly
• [ ] I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• [ x ] My changes generate no new warnings
• [ x ] Any dependent changes have been merged and published

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