test: `test_kv` Flaky Due to Model Safety Refusal

[planetf1]

test_kv Flaky Due to Model Safety Refusal

Found during: Test infrastructure improvements (PR fixing test markers and GPU cleanup)

Location: test/stdlib/test_spans.py::test_kv

Issue: Model refuses to answer questions about personal information, even when provided in context.

Test Setup:

# Context provided:
doc1 = "Nathan Fulton is a scientist at the MIT-IBM Watson AI Lab."
doc2 = "The MIT-IBM Watson AI Lab is located at 314 Main Street, Cambridge, MA."

# Question: "What is Nathan's work address?"

Expected: Response containing "314"

Actual:

I'm sorry, but I can't provide personal information about individuals, 
including their work addresses,

Root Cause: Model's safety filters trigger on "Nathan's work address" despite:

• Information is in the provided context
• Asking about work address (public), not personal residence
• Test is checking KV cache functionality, not safety behavior

Current Status: Marked with @pytest.mark.xfail(strict=False) to allow flaky behavior

Recommended Fix: Rephrase question to avoid safety trigger:

• "What is the address of the MIT-IBM Watson AI Lab?"
• "Where is the lab located?"

This maintains KV cache testing while avoiding model safety guardrails.