57 — Progressive overload (replace hard overweight gate)

Status: implemented (sim + clients + Settings). Mass is not a pickup reject.

Product owner: Barry.

Locked rules (shipped):

1. No hard “too heavy to carry” on player mass-gaining paths. Volume stays hard.
2. Continuous curve on r = mass/capacity; never fully immobile (min_speed_mult 0.012).
3. UI bands: Green r ≤ 0.95, Yellow ≤ 1.25, Orange ≤ 2.0, Red above. Wire enum: Light / Heavy / Orange / Over.
4. Knobs in inventory: + content-admin Settings.
5. Hunger/thirst faster while overloaded even standing; stamina drain only while moving.
6. Strength XP: CarryExertion distance + multiplier on other STR events when r > 1.
7. Anti-circle: CarryExertion only while stamina > 0 and moved; strength_xp_max_per_min 0.20; needs_at_capacity 1.5 / needs_at_immobile 4.0; strength_xp_meters 8; carry_base_xp 0.006; strength_xp_per_over_ratio 0.4.
8. No sprint in Red; Orange sprint with ×1.5 extra encumbrance stamina burn.
9. Workers: same curves; job AI still unloads ~90–95%; companions skip pickup at the soft line.
10. Clients color mass Green/Yellow/Orange/Red; no client mass clamp on transfers.

See docs/progressive-overload.md and specification §3.2.