feat: enhance token usage resolution for OpenAI and Anthropic compati…

[AlapinEnjoyer]

Description

Cached token usage was not getting tracked for the OpenAI provider, the MR adds a way to recognize the common OpenAI-compatible cached-token fields for custom providers

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactoring (no functional changes)
• Documentation update
• CI / Build / Tooling

How Has This Been Tested?

• make test passes locally
• Manual testing (describe below)

Tested with a custom provider run

Checklist

• My code follows the project's coding style (go fmt, go vet)
• I have performed a self-review of my code
• I have added tests that prove my fix is effective or my feature works
• New and existing unit tests pass locally with my changes
• I have updated the documentation accordingly (if applicable)
• I have signed the CLA

[github-actions]

🔍 OpenCodeReview found 1 issue(s) in this PR.

• ✅ 1 posted as inline comment(s)
• 📝 0 posted as summary

[github-actions]

Minor maintainability issue: These two new entries lack comments describing which providers or API formats use cache_creation_tokens under prompt_tokens_details. All other entries in these path lists have explanatory comments. Adding a comment (e.g., // OpenAI-compatible providers or similar) would keep the style consistent and help future maintainers understand when this path applies.

Suggestion:

Suggested change

	"usage.prompt_tokens_details.cache_creation_tokens",
	"data.usage.prompt_tokens_details.cache_creation_tokens",
	"usage.prompt_tokens_details.cache_creation_tokens", // OpenAI-compatible providers
	"data.usage.prompt_tokens_details.cache_creation_tokens", // wrapped OpenAI-compatible providers