Motivation

Follow-up to #3881 and #3882. The vector scoring functions each have fragile positional overloads:

• vectorRRFScore(rank1, rank2, ... [, k]) - ambiguity: a trailing Number >= 60 is treated as k, otherwise as a rank list. Adding weights or normalize later would multiply the ambiguity.
• multiVectorScore(scores, method [, weights]) - the weights slot is only valid when method == "WEIGHTED".
• vectorHybridScore(vec, kw, alpha) - no options today, but foreseeable normalize, method, kwMax, vecMax.

Proposal

Accept a trailing options map validated by FunctionOptions on each function. Legacy positional forms remain supported. Unknown keys are rejected.

Deliverables

• Code: route trailing options through FunctionOptions.
• Tests: options-map path + unknown-key rejection.
• Docs: show options-map syntax alongside the positional form.