[TST-E4] SDK contract tests become tables with scenario builders #492

Part of #350, the quality-refactoring roadmap (road to 1.0, step 3).

Goal: SDK contract tests become tables with scenario builders (one declared-error table instead of 129 methods).

Lane: Tests. Status: active. Merged so far: #446, #458, #460, #463, #464, #467, #474, #479.

Every PR of this epic starts its title with [TST-E4]. The finding issues it closes are linked as sub-issues; this issue closes when the epic's last PR merges and master CI is green.