fix(lods): remove incorrect BUN >= 7.50 renal point

[acnimma]

Summary

• Remove the erroneous bun_max >= 7.50 THEN 1 branch from MIMIC-III and MIMIC-IV lods.sql
• Mirror the deletion in postgres and duckdb dialect copies
• Document intended BUN mg/dL cutoffs (17 / 28 / 56) beside the renal CASE so a mmol/L-style arm is not reintroduced

Why

Le Gall et al. (JAMA 1996) score serum urea nitrogen as:

• 0 for BUN < 17 mg/dL
• 1 for 17–27
• 3 for 28–55
• 5 for ≥56

MIMIC stores BUN in mg/dL. The extra >= 7.50 arm incorrectly awarded renal points for BUN ~7.5–16.9 (and sat under the >= 17 check in the same CASE).

Test plan

• No 7.50 threshold remains in any lods.sql
• Inline comment cites Le Gall mg/dL cutoffs next to renal scoring
• LODS renal: BUN 10 → 0; BUN 20 → 1; BUN 30 → 3; BUN 60 → 5 (when other renal inputs allow)

Fixes #1065

[Chessing234]

this tracks — that >= 7.50 arm was sitting under the >= 17 check so it was quietly giving renal points for bun ~7.5–16.9, which isn't in le gall. deleting it is cleaner than rewriting thresholds. good that you hit both iii and iv + dialects.

[Chessing234]

that bun >= 7.50 arm looks like a unit mixup. glad it's gone — maybe add a one-line comment with the intended mg/dl cutoff.

[Chessing234]

the bun_max >= 7.50 arm was unreachable under bun_max >= 17.0 in the same case, so deleting it is correct for lods. mirrored across iii/iv and all dialects — nice. a short pr note citing the lods paper threshold table would help reviewers who weren't in the original bug report.

[acnimma]

Added an inline note beside the renal CASE documenting the Le Gall BUN cutoffs in mg/dL (0 if <17, 1 if 17–27, 3 if 28–55, 5 if ≥56) and warning not to reintroduce mmol/L-style arms like 7.50.

Mirrored in MIMIC-III + MIMIC-IV BigQuery sources and the postgres dialect copies (duckdb transpile drops comments by design). PR body already cites Le Gall et al., JAMA 1996.