j160 (default-off): the energy-reserve FIRING FLOOR + ENEMY-EXHAUSTION ram trigger

TR_RAM_FLOOR_ENERGY (0.0 = off): at/below this self energy we start no NEW
shot, holding back the reserve for a final ram exchange. Justified by the only
energy gain in the game being +3*power per bullet hit LANDED, so not firing
denies the enemy its only refill. Blocks only NEW shots (gunHeat already gates
committed ones) and is bypassed while ramming.

TR_RAM_ENEMY_ENERGY (0.0 = off): last-scanned enemy energy <= this -> ram
mode. Enemy energy IS observable (ScannedBotEvent.energy, schemas.nim:306),
1-8 ticks stale. This is the shipped finisher with its energy tolerance
promoted to a knob, keeping the self>enemy surplus guard because RAM_DAMAGE
0.6 applies to BOTH bots on every contact tick.

Open-loop measurement (measure_ramfloor_energy, 8149 recordings / 29871
rounds / 33.8M ticks): 'both low' is COMMON (10.4% of ticks below 20, 15.1%
below 25) but neither side goes low first (enemy 52.7% / us 47.3%), and the
owner's literal trigger - enemy so low it cannot fire (energy <= 1.95) - is
only 2.5% of ticks, 1.1% while we are healthy.

Guards 136 -> 147 in test_tfil_commit_env.nim, all green. A/B PRE-REGISTERED
in docs/ram_floor_exhaustion_ab.md and NOT RUN.

common_libs/movements/ram_decision.nim

@@ -46,7 +46,29 @@
 ##   TR_RAM_PLAN_MARGIN   default 20.0   change-of-plan energy advantage
 ##   TR_RAM_PLAN_HITRATE  default 0.05   selected gun's pooled virtual hit rate
 ##                                       below which the gun duel counts as failing
-##   TR_RAM_LOG=1                        emit one change-gated `[ram]` line
+##   ##   TR_RAM_LOG=1                        emit one change-gated `[ram]` line
+  ##   TR_RAM_FLOOR_ENERGY default 0.0    FIRING FLOOR (j160). At or below this
+  ##                                      self energy we stop firing to keep a
+  ##                                      ram reserve. 0 = off = today's behaviour.
+  ##   TR_RAM_ENEMY_ENERGY default 0.0    ENEMY-EXHAUSTION trigger (j160). The
+  ##                                      last-scanned enemy energy <= this ->
+  ##                                      ram mode. 0 = off.
+##
+## ── j160: the energy-reserve + exhaustion policy ───────────────────────────
+## Energy NEVER regenerates and has no cap; the only gain in the whole game is
+## `+3 * power` per bullet hit LANDED (server `rules.kt`). So not firing denies
+## the enemy its only refill AND keeps our ram reserve intact — the two halves
+## of the policy are the same bet.
+##
+## Floor sizing: one likely return hit (`bulletDamage(1.0)` = 4.0) plus two
+## 0.1-power shots (0.1 each) is 4.2. The knob DEFAULT stays 0.0 so the default
+## path is byte-identical; the operator sets 5-ish.
+##
+## The exhaustion trigger is the FINISHER with the energy tolerance promoted to
+## an operator knob. It deliberately KEEPS the finisher's own
+## `selfEnergy > enemyEnergy` surplus guard: `RAM_DAMAGE 0.6` is applied to BOTH
+## bots on every contact tick, so a head-on contact is a symmetric bleed decided
+## by who walks in with the surplus.
 
 import std/[os, strutils]
 
@@ -95,10 +117,15 @@ let RamPlanDist*    = getEnvFloat("TR_RAM_PLAN_DIST",   DefaultRamPlanDist)
 let RamPlanMargin*  = getEnvFloat("TR_RAM_PLAN_MARGIN", DefaultRamPlanMargin)
 let RamPlanHitRate* = getEnvFloat("TR_RAM_PLAN_HITRATE", DefaultRamPlanHitRate)
 let RamLog*         = existsEnv("TR_RAM_LOG")
+## j160. 0.0 = off on BOTH knobs, which is the shipped behaviour.
+let RamFloorEnergy*  = getEnvFloat("TR_RAM_FLOOR_ENERGY", 0.0)
+let RamEnemyEnergy*  = getEnvFloat("TR_RAM_ENEMY_ENERGY", 0.0)
 
 type
   RamReason* = enum
     rrNone        ## no trigger fires
+    rrExhausted   ## j160: last-scanned enemy energy <= TR_RAM_ENEMY_ENERGY
+    ##              and we hold the surplus (it is out of ammo, we are not)
     rrFinisher    ## enemy < 20 energy, we are healthier, dist < 300
     rrOpportunity ## we clearly out-energise and are close enough to close
     rrDesperation ## both nearly dead, short range
@@ -131,7 +158,8 @@ proc ramTrigger*(inp: RamInputs,
                  planEnabled = RamPlanEnabled,
                  planDist = RamPlanDist,
                  planMargin = RamPlanMargin,
-                 planHitRate = RamPlanHitRate): RamReason =
+                 planHitRate = RamPlanHitRate,
+                 enemyEnergyTol = RamEnemyEnergy): RamReason =
   ## Pure trigger evaluation. Returns the FIRST matching reason in priority
   ## order, or `rrNone`. Cooldown/duration/abort are deliberately NOT here — the
   ## caller composes those, so this function has no state and is unit-testable.
@@ -143,6 +171,13 @@ proc ramTrigger*(inp: RamInputs,
   ## `desperation` and `finisher` are kept: they are rare, short-range, and the
   ## finisher is the only measured conversion. `plan` remains opt-in and off.
   if inp.enemyEnergy <= 0.0: return rrNone
+  # j160 exhaustion trigger. Checked FIRST so the operator-set tolerance wins
+  # the label when it is set; it is the finisher's own shape (same surplus and
+  # distance guards) with the 20.0 energy tolerance promoted to a knob. With
+  # `enemyEnergyTol = 0.0` (the default) this arm can never fire.
+  if enemyEnergyTol > 0.0 and inp.enemyEnergy <= enemyEnergyTol and
+     inp.dist < RamFinisherDist and inp.selfEnergy > inp.enemyEnergy:
+    return rrExhausted
   if inp.dist < RamFinisherDist and inp.enemyEnergy < RamFinisherEnergy and
      inp.selfEnergy > inp.enemyEnergy:
     return rrFinisher
@@ -158,9 +193,24 @@ proc ramTrigger*(inp: RamInputs,
     return rrPlan
   rrNone
 
+proc fireFloorBlocks*(floor, selfEnergy: float, ramming = false): bool =
+  ## j160 FIRING FLOOR. True when the reserve is thin enough that we must not
+  ## commit a NEW shot. `floor = 0.0` (the default) disables the floor entirely
+  ## and returns false for every input, so the default path is unchanged.
+  ##
+  ## `ramming` WINS over the floor: once ram mode is engaged the duel is over,
+  ## so the reserve is being spent on the contact, not held for it. This is the
+  ## same exemption `ramming` already gets in `applyPowerPolicy`.
+  ##
+  ## The floor blocks only NEW shots. A bullet already in the air (gun heat > 0)
+  ## is untouched — `shouldFire` already gates on `gunHeat <= 0.0`, so there is
+  ## no committed shot for the floor to suppress or cancel.
+  not ramming and floor > 0.0 and selfEnergy <= floor
+
 proc reasonName*(r: RamReason): string =
   case r
   of rrNone:        "none"
+  of rrExhausted:   "exhausted"
   of rrFinisher:    "finisher"
   of rrOpportunity: "opportunity"
   of rrDesperation: "desperation"