remove "preparing model request params" span

[samuelcolvin]

No description provided.

[Copilot]

Pull Request Overview

This PR removes the "preparing model request params" span from the logging/tracing and updates associated snapshots and attributes in tests.

• Removed the "preparing model request params" span from the children list in tests/test_logfire.py.
• Updated span names, attributes, and timing (end_time) in tests/models/test_fallback.py to reflect the change.
• Removed the tracer span block from pydantic_ai_slim/pydantic_ai/_agent_graph.py.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tests/test_logfire.py	Removed span entries and updated the attributes index to align with the modified children list.
tests/models/test_fallback.py	Updated span names, adjusted attribute structure (e.g. events format) and modified end_time values; also removed an unused import.
pydantic_ai_slim/pydantic_ai/_agent_graph.py	Removed the tracer span block related to the "preparing model request params" span.

Comments suppressed due to low confidence (4)

tests/test_logfire.py:161

• Verify that updating the chat span attributes index from [2] to [1] is intentional and that all dependent assertions have been adjusted accordingly.

chat_span_attributes = summary.attributes[1]

tests/models/test_fallback.py:119

• [nitpick] Ensure that the span name 'chat function:success_response:' uses the intended colon pattern and that it is consistent with naming conventions in other spans.

'name': 'chat function:success_response:'

tests/models/test_fallback.py:189

• [nitpick] Consider aligning the colon usage in the span name with that of similar spans to avoid confusion; the double colon here may be unintentional.

'name': 'chat function::success_response_stream',

tests/models/test_fallback.py:143

• Confirm that the adjustment of the end_time value from 6000000000 to 4000000000 is correct according to the updated timing logic.

'end_time': 4000000000,

[github-actions]

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