fix: don't trace injected args only found in signature

[sydney-runkle]

for the case when they're not included in the args_schema

this was predicted by @eyurtsev's comment here: https://github.com/langchain-ai/langchain/pull/33729/files#r2475538173

pairing w/ this PR in mcp adapters: langchain-ai/langchain-mcp-adapters#407

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing why-tracing-runtime (9eecf29) with master (2847814)¹}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 13 untouched benchmarks
⏩ 21 skipped benchmarks²

Footnotes

1. No successful run was found on master (76da99e) during the generation of this report, so 2847814 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 21 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩