[SWEEPS] One per-unit sweep PR for each group of small findings that no epic covers #498

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

Goal: One per-unit sweep PR for each group of small findings that no epic covers.

Lane: All lanes. Status: active. Merged so far: #395, #396, #397, #420, #468, #471.

Every PR of this epic starts its title with [SWEEPS]. 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.