Legs I-frames on Jump

WHAT IT DOES
------------
When you jump, your legs become invulnerable for a short window
mid-air. Any attack — melee, projectile —
that touches the leg zone is completely nullified (no damage,
no knockback, no sound, no stagger if user has an epic fight). The rest of your body
stays fully vulnerable the entire time.

The leg zone is the bottom 0.70 blocks of your hitbox (from feet).
The i-frame window opens 2 ticks after the jump and lasts 12 ticks
(0.6 seconds). Fall damage is NOT affected.(fully configurable).

any other parts of body get 15% increased damage during i-frames.

HIT DETECTION
-------------
- Players:   The attacker's swing path is traced through your
             hitbox (entry + exit points). If ANY part of thatin
             path dips into the leg zone, the entire hit is
             nullified — even if the swing also crosses the torso.

- Mobs:      The mob's eye height is clamped to your hitbox
             range. A short zombie vs an airborne player only
             reaches the legs; a tall golem still hits the body.

- Projectiles: If the exact impact point is below the leg zone
             top, the projectile passes straight through.

JUMP BOOST
----------
Adds a small velocity boost on every jump.
Default: +0.020  =>  apex ~1.366 blocks  (~1 pixel above vanilla)
Vanilla:  0.000  =>  apex ~1.252 blocks

EPIC FIGHT COMPATIBILITY  (optional soft dependency)
----------------------------------------------------
- Collider scaling:all default weapon-type
  colliders are resized to x=0.1, y=0.2, z*1.2. This makes
  weapon hitboxes narrower and slightly longer.

- Stagger cancel: Epic Fight staggers triggered by leg-zone hits
  are cancelled via the same swing-path model as damage.

- Stamina cost: jumping costs 1.5 stamina ONLY within 12 seconds
  of taking damage. Outside that window, jumps are free.

CONFIGURATION  (leg_iframes_on_jump-common.toml)
-------------------------------------------------
iframeDuration      12      ticks the leg i-frames last
iframeDelay          2      ticks after jump before window opens
legFraction        0.5      fraction of body height = legs
                            (0.5 * 1.8 - 0.2 = 0.70 blocks)
jumpBoost          0.020    extra upward velocity on jump

[colliderScaling]
scaleEpicFightColliders   true
colliderSizeX             0.1    absolute half-width
colliderSizeY             0.2    absolute half-height
colliderScaleZ            1.2    reach multiplier