fix(recall): preserve vector fetch limit floor

[jack-arturo]

Summary

• Preserve the caller's requested vector fetch limit even when RECALL_VECTOR_FETCH_CAP is configured below limit.
• Add a regression test for the cap-under-limit edge case.
• Keeps the cap as an over-fetch ceiling without allowing it to make recall narrower than legacy behavior.

Context

Follow-up to PR #205. The original over-fetch implementation used min(per_query_limit * RECALL_VECTOR_OVERFETCH, RECALL_VECTOR_FETCH_CAP), which can ask Qdrant for fewer candidates than the requested response limit when the cap is set low.

Tests

• venv/bin/pytest tests/test_recall_overfetch.py tests/test_recall_artifact_exclusion.py
• make test
• A/B already run locally while evaluating PR fix(recall): over-fetch vector candidates and exclude artifact types #205:
  • locomo-mini: main 82.98% (195/235) -> PR 84.26% (198/235)
  • locomo: main 81.58% (1258/1542) -> PR 81.84% (1262/1542)

Risk Notes

• This is a narrow guardrail around the new config; it should only affect deployments that lower RECALL_VECTOR_FETCH_CAP below requested limit.
• No merge performed.

[jack-arturo]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Can't wait for the next one!

Reviewed commit: 833cbbb558

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".