Optional types for GPT-OSS models

[thatsKevinJain]

GPT-OSS now supports both Responses and Chat/Completions formats, this
will allow users to get type completions for both of them.

[codspeed-hq]

Merging this PR will degrade performance by 11.57%

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 68 untouched benchmarks
⏩ 129 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	Encode_ASCII_32[TextEncoder][0/0/32]	3.4 ms	3 ms	+13.1%
❌	simpleStringBody[Response]	19.1 µs	21.6 µs	-11.57%

---

_{Comparing thatsKevinJain:kevin/ai-xor-types (34b372b) with main (fd62891)}

Footnotes

1. 129 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. ↩