add notes on ... #69

Moved from UCD-SERG/lab-manual#268 (opened by d-morrison on 2026-05-18); it belongs in the coding-practices chapter. (The original had 4 comments; see the link back for the discussion.)

• don't manually define ... when inheritDotParams would do the trick
• don't unnecessarily intercept and relay arguments that could just be passed through to a subfunction using ...
• validate arguments once they reach the function where they will be actually used