fix: configure Nvidia reranker truncation

[erichare]

What this PR does:

• Add a validated model-level reranker truncate setting.
• Configure Nvidia with END and use it in provider requests.
• Keep NONE explicit when the setting is unavailable.

Which issue(s) this PR fixes: Fixes #2568

Checklist

• Changes manually tested
• Automated Tests added/updated
• Documentation added/updated
• CLA Signed: DataStax CLA

[github-actions]

📈 Unit Test Coverage Delta vs Main Branch

Metric	Value
Main Branch	53.44%
This PR	53.55%
Delta	🟢 +0.11%
✅ Coverage improved!

[github-actions]

Unit Test Coverage Report

Overall Project	53.55%	🍏
Files changed	79.17%	🍏

File	Coverage
NvidiaRerankingProvider.java	98.81%	🍏
RerankingProvidersConfigImpl.java	78.57%	🍏
RerankingProvidersConfig.java	47.37%	🍏
RerankingProviderConfigProducer.java	32% -1.67%	❌

[github-actions]

📈 Integration Test Coverage Delta vs Main Branch (dse69-it)

Metric	Value
Main Branch	71.45%
This PR	71.45%
Delta	🟢 +0.00%
✅ Coverage improved!

[github-actions]

Integration Test Coverage Report (dse69-it)

Overall Project	71.45% -0.01%	🍏
Files changed	62.5%	🍏

File	Coverage
RerankingProvidersConfig.java	98.68%	🍏
RerankingProviderConfigProducer.java	32% -1.67%	❌
RerankingProvidersConfigImpl.java	28.57%	🍏
NvidiaRerankingProvider.java	12.5% -2.38%	❌

[github-actions]

📉 Integration Test Coverage Delta vs Main Branch (hcd-it)

Metric	Value
Main Branch	72.76%
This PR	72.76%
Delta	🔴 -0.00%
⚠️ Coverage decreased

[github-actions]

Integration Test Coverage Report (hcd-it)

Overall Project	72.76% -0.01%	🍏
Files changed	62.5%	🍏

File	Coverage
RerankingProvidersConfig.java	98.68%	🍏
RerankingProviderConfigProducer.java	32% -1.67%	❌
RerankingProvidersConfigImpl.java	28.57%	🍏
NvidiaRerankingProvider.java	12.5% -2.38%	❌

[amorton]

-1 , have not reviewed but we need PRs to follow the template pls

https://github.com/stargate/data-api/blob/main/.github/pull_request_template.md