Stabilize pkg/ai coverage runs and eliminate lingering httptest shutdown/coverage export flakiness

[CodeMonkeyCybersecurity]

Summary

pkg/ai functionally passes its targeted tests after the #291 fix, but package-level coverage runs still show shutdown/coverage-export instability.

Evidence

• go test -cover ./pkg/ai reported httptest.Server blocked in Close after 5 seconds.
• The same run then failed with error generating coverage report ... gocoverdir ... no such file or directory.
• The behavior is separate from the original invalid-URL timeout issue, which is now fixed by fail-fast URL validation.

Why this matters

• It makes the package look unhealthy even when the functional regression is fixed.
• It undermines confidence in coverage-based gates and developer feedback loops.

Proposed work

1. Audit pkg/ai tests for response bodies or idle connections that are not drained/closed under all paths.
2. Reproduce the coverage-export failure under the current Go toolchain and isolate whether it is test behavior or toolchain interaction.
3. Add a targeted regression test for the timeout path that is compatible with coverage runs.
4. Document any required harness changes if the issue is Go-version-specific.

Acceptance criteria

• go test -cover ./pkg/ai passes reliably.
• No httptest.Server blocked in Close warning appears in the package test run.
• Coverage artifacts are produced consistently for pkg/ai.