fix: remove spurious repair_json call in _validate_tool_input that could skip Attempt 3

[SinzoL]

In _validate_tool_input(), Attempt 2 (ast.literal_eval) has an except branch that calls repair_json(tool_input). This variable is never read before Attempt 4 reassigns it, making it dead code. Worse, if repair_json itself raises, Attempt 3 (json5) is skipped entirely. Replace with pass. Fixes #4851

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Note

Low Risk
Low risk, small control-flow change limited to tool argument parsing; it mainly prevents an unnecessary repair_json invocation from skipping the JSON5 parse path if it raised.

Overview
Fixes tool input parsing control flow. In ToolUsage._validate_tool_input, the ast.literal_eval failure path no longer calls repair_json (dead code), so failures proceed cleanly to the JSON5 parse attempt before the final JSON repair step.

This avoids repair_json exceptions prematurely bypassing Attempt 3 and makes parsing behavior more predictable.

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