actg: str2 and treat duplicate strat and trt #141

Problem

Two actg features are functions of other features:

• str2 (antiretroviral history, 0 naive or 1 experienced) is exactly strat > 1 for every patient.
• treat (0 ZDV only, 1 other arms) is exactly trt > 0 for every patient.

A method can acquire the same information twice at twice the cost, and the feature count overstates what the dataset holds.

Scope

• Dataset generation for actg; both budget settings.
• Changes paper results if features are dropped: actg is in the kdd26 dataset list.

Options to decide

• Drop str2 and treat, keeping the finer strat and trt.
• Or keep all four as UCI ships them and state the redundancy on the dataset page.

Acceptance criteria

• actg follows the decision, and docs/reference/datasets/actg.md states it.
• just qa passes.