Degrade retrieval to test CI gate

[NaveenBuidl]

Intentional degradation PR to verify the eval CI gate blocks lower retrieval quality.

Changes:

• retrieval_k: 4 -> 1
• retrieval_k: 1 -> 0

Expected:

• Eval Gate should fail if retrieval quality drops or retrieval becomes invalid.

[Copilot]

Pull request overview

This PR intentionally degrades retrieval configuration to validate that the evaluation CI gate fails when retrieval quality drops or retrieval becomes invalid.

Changes:

• Comments out the prior retrieval_k: 4 value.
• Sets retrieval_k to 0 in config.yaml.

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[Copilot]

Setting retrieval_k: 0 is likely to make retrieval invalid: app/rag.py passes this directly as n_results to Chroma’s collection.query, which commonly requires n_results >= 1 and may raise at runtime (failing CI for a crash rather than an eval-quality regression). If the goal is to degrade quality while keeping the pipeline valid, set this to 1 instead; if the goal is to test invalid config handling, consider adding explicit validation (fail fast with a clear error) rather than relying on downstream library behavior.