Normalize ammo economy: per-weapon refill, stream drain, behavior fixes

- Every special weapon gets an explicit 'refill' (units per ammo pickup,
  tuned so one pickup funds ~10 kills) replacing the ammoRefillFraction
  log2 heuristic and ammoWeight overrides
- Bile Blunderbuss + The Cauterizer join Red Right Hand as time-denominated
  stream weapons ('drain' per second) instead of per-shot cost
- Sawblades ricochet through enemies (bounce fix), traps catch 3 victims,
  lobbed projectiles arc overhead and always trigger at the target point
  (Flesh Masher / Trap Queen / Swarm Jar payloads now actually deploy)
- Boss rooms stock one ammo on entry and drop one guaranteed on death
- Cauterizer burn trimmed (2.2s x2 -> 1.5s x0.8), bile acid pools trimmed
  (3.5s x1.5 -> 2.5s x0.8), Marrow Draught now covers stream drain
- New tools/ammo_sim.js calibrates every weapon into the 8-13 kills/refill
  band (all 15 pass); smoke test guards the ammo structure
- v0.3.0, cache bump v=44

js/state.js

@@ -45,8 +45,7 @@ const G = {
 };
 
 const PERK_POWER_WEIGHT = 0.5;
-// ammo economy: global dials for refill size and drop frequency
-const AMMO_REFILL_SCALE = 0.75;
+// ammo economy: global dial for drop frequency (refill size is per-weapon)
 const AMMO_DROP_SCALE = 0.75;
 const PRESSURE_MIN = 0.75, PRESSURE_MAX = 1.60;
 const PRESSURE_UNIT = 0.01;          // one "point" on the dial scale