fix: add warning log when tool input JSON parsing fails

[Zelys-DFKH]

Description

When a model returns tool input that cannot be parsed as JSON, the SDK silently falls back to an empty dict. This makes it impossible to distinguish between a tool that legitimately received {} from the model and one that received unparseable content.

This change adds a WARNING log before the fallback that includes the tool name and the first 200 characters of the raw input, making the silent failure observable in logs.

Related Issues

Fixes #2051

Documentation PR

N/A

Type of Change

Bug fix

Testing

Added test_handle_content_block_stop_invalid_json_logs_warning to tests/strands/event_loop/test_streaming.py. The test verifies that when handle_content_block_stop encounters invalid JSON tool input, it falls back to {} and emits a warning log containing "failed to parse tool input as JSON".

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• 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
• My changes generate no new warnings
• Any dependent changes have been merged and published

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