fix(core): handle missing StructuredPrompt schema

[baskaryan]

• Description: if you dont pass in schema= or schema_= to StrucutredPrompt(...) today you get a confusing KeyError. Raise a more readable ValueError instead.
• Issue: na
• Dependencies: na

[codspeed-hq]

CodSpeed Performance Report

Merging #34096 will not alter performance

_{Comparing bagatur/struct_prompt_init_nit (381893c) with master (880652b)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
⏩ 21 skipped²

Footnotes

1. No successful run was found on master (9c21f83) during the generation of this report, so 880652b 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. ↩