feat: dash ability; ammo pressure scaling, full-HP hearts, muzzle alignment, holstered debug ammo

- Shift dash: 0.45*v*0.6 instant burst then 0.6s of 50% slow (net 95% of
  walking distance); slow doubles as cooldown, no dash while idle/slowed.
- Generic ammo refills scale with the live pressure dial at 80% of the HP
  multiplier via ammoPressureMul().
- Hearts at full HP stay on the floor (magnet ignores them) instead of
  converting to score.
- Muzzle audit: flame FX and pellets share one right-hand origin, Spinal
  Tap beam starts at the muzzle, saw flash suppressed (blade sparks are
  the effect).
- Debug REFILL/INF AMMO and the ammo row now cover a spent special
  holstered behind the Bone Popper.
- Sfx.duck() defaults its args; a no-arg call crashed the loop with a
  non-finite AudioParam value (found via the dash E2E).

js/state.js

@@ -61,6 +61,8 @@ const G = {
 const PERK_POWER_WEIGHT = 0.5;
 // ammo economy: global dial for drop frequency (refill size is per-weapon)
 const AMMO_DROP_SCALE = 0.75;
+// Generic ammo refills track the live pressure dial at 80% of the HP scaling.
+function ammoPressureMul() { return 1 + (G.pressure - 1) * 0.8; }
 const STUN_UNIT = 0.03 / 0.97; // Sine Weave raw rating per stack, so the first stack = 3% stagger chance
 const PRESSURE_MIN = 0.60, PRESSURE_MAX = 2.00;
 // seconds a player-dropped weapon stays un-pickable (prevents instant swap loops)