fix: add NVIDIA API host to reasoning_content allowlist for DeepSeek V4 models

[SnotacusNexus]

Summary

• Adds integrate.api.nvidia.com to the reasoning_content allowlist so DeepSeek models (deepseek-ai/deepseek-v4-flash, deepseek-ai/deepseek-v4-pro) hosted on NVIDIA's API don't get a 400 error on tool-call rounds
• Adds a history-based fallback (hasThinkingBlockInHistory) so unlisted providers that already returned a thinking block continue to echo reasoning_content correctly
• Adds providerSupportsReasoning() as a unified entry point combining explicit host matching + history detection, with a carve-out for api.openai.com to avoid false positives

Impact

• user-facing: fixes API Error: 400 {"error":{"message":"The reasoning_content in the thinking mode must be passed back to the API."}} when using DeepSeek models (deepseek-ai/deepseek-v4-flash, deepseek-ai/deepseek-v4-pro) through integrate.api.nvidia.com
• developer/maintainer: the two-pronged approach (allowlist + history heuristic) means new reasoning providers work without code changes as long as they already returned a thinking block on the first response

Testing

• bun run build
• bun run smoke
• focused tests: bun test src/services/api/openaiShim.test.ts — blocked by pre-existing bun:bundle import issue in slowOperations.ts

Notes

• provider/model path tested: NVIDIA API (integrate.api.nvidia.com) with deepseek-ai/deepseek-v4-flash and deepseek-ai/deepseek-v4-pro
• follow-up work or known limitations: none

[jatmn]

#910 adds per provider/gateway flags for this i think. or at least has the framework to adapt it cleanly.
I would test you change concepts against that pr and see if it works or not.

[gnanam1990]

Nice — adding NVIDIA's integrate.api.nvidia.com to the allowlist and the unified providerSupportsReasoning() helper is a clean refactor. Explicit api.openai.com carve-out to avoid false positives is a good touch.

LGTM. Once the bun:bundle smoke is unblocked, a small unit test for hasThinkingBlockInHistory would be a nice follow-up.

[kevincodex1]

hello bro @SnotacusNexus we just merged the registry PR for providers, kindly fix conflicts and this is good to go

[Vasanthdev2004]

Targeted maintainer triage review of the current head ($short).

Verdict: Needs changes

Blocking issue:

1. GitHub reports this branch as DIRTY / conflicting with main, so it cannot be merged or final-approved as-is. Please rebase or merge latest main, resolve the conflicts, and rerun the relevant checks.

I did not do a full code review because the current branch state is not mergeable. Happy to re-review once the branch is clean.