⚡ Dexterity calculation

"Time per attack" is the cooldown between two swings. Sphere calls
it "swing delay" — same thing.

This sphere build's combat formula isn't public. The calculator uses
an empirical model built from .swing_meter measurements on three
weapons: SPEED 56 dagger, SPEED 28 viking sword, SPEED 40 mace.

Model:
  active(DEX, SPEED) = refDelay(DEX) × 56 / SPEED
  delay              = max(0.4 s, active)

The "active" part scales inverse-linearly with SPEED — so for a
slower weapon you need more DEX to reach the same speed. The
absolute floor of 0.4 s is sphere's hard minimum and applies
regardless of weapon SPEED (verified at SPEED 40 DEX 3500 = 0.4 s
which would otherwise be 0.56 s with pure scaling).

Reference curve at SPEED 56 (linearly interpolated between):

  DEX    80  →  1.35 s
  DEX   100  →  1.20 s
  DEX   150  →  1.10 s
  DEX   250  →  0.90 s
  DEX   350  →  0.80 s
  DEX   450  →  0.70 s
  DEX   550  →  0.60 s
  DEX   800  →  0.50 s
  DEX  1500  →  0.40 s
  DEX  2000+ →  active drops to 0 (the 0.4 s floor takes over)

Slower weapons need more DEX to floor — e.g. SPEED 28 viking sword
floors around DEX 3000 (not 1500). The faster the weapon, the
sooner you saturate.

Special case: wrestling (SPEED 0) ignores all of this — sphere
uses a fixed internal wrestling timer (~1.4 s regardless of DEX).