j141 fix: the per-gun real-shot accounting was still array[17] after rack id 17 landed

REGRESSION: the live bot stopped firing entirely and moved degenerately
whenever a rack admitted rack id 17 (the ADE+SBC BITBRAIN gun added in
e9302bc).

ROOT CAUSE: ModularBot.nim declared the per-gun accounting arrays
(gunRealShots / gunRealHits / gunRealShotsByMode / gunRealHitsByMode /
gunSelectionCount) as array[17, int] — the rack size BEFORE id 17 existed.
The instant the selector picked gun 17, the accounting indexed one past
the end:

  * debug build -> IndexDefect out of run(): the bot stops, 0 shots;
  * -d:release (shipped) -> silent out-of-bounds write onto the adjacent
    lastPowerLogKey: string header, so the bot kept moving but never
    fired and never reported a shot.

Measured with the owner's exact out/.env, 1v1 SittingDuck:
  0dc5552 (pre-rename):  BitBrain(id16) selected 356+157 ticks,
                         realShots 24+9, realHits 23+9,  ModularBot wins 180/360
  HEAD (e9302bc..)   :  selected 0, vShots 0, realShots 0, realHits 0
  debug               : IndexDefect on the first tick that selects id 17
  -d:release         : same 0/0/0, bot scores 22 and dies

FIX: derive every gun-indexed width from the rack instead of a literal.
gun_harness/selector exports NumRackGuns* = len(RackGunNames) (18);
ModularBot uses it for the five accounting arrays, the per-round reset
loops, the gun_stats.jsonl dump loop, the  table and
initTracker(). Shipped defaults unchanged: clean env is still the
onlyPattern rack and movement is still strafe.

GUARD: common_libs/tests/test_rack_stat_width.nim (24 checks) — rack
table shape, a source scan proving no gun-indexed width/loop bound is
narrower than NumRackGuns, an in-process accounting replay that would
have overflowed array[17], and the legacy-namespace checks (id 16 via
TR_RACK_BITBRAIN, id 17 never admitted while legacy). It reports 7
failures on the pre-fix ModularBot.nim and passes after. Optional
--live section proves a rack admitting only the newest id fires and
lands hits.

Parity: test_env_report 25, test_rack_membership 49, test_lead_gain_
registration 13, test_lead_gain_legacy 24, test_bitbrain_net 44,
test_gun_harness 39, test_tfil_commit_env 30, test_bitbrain 56,
test_tm_pattern_registration 20 — all unchanged, 0 failures.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ModularBot_garage/src/ModularBot.nim

@@ -286,18 +286,24 @@ type
     roundNumber:  int
     realShotsFired: int
     realHits:     int
-    gunRealShots: array[17, int]
-    gunRealHits:  array[17, int]
+    gunRealShots: array[NumRackGuns, int]
+    gunRealHits:  array[NumRackGuns, int]
     # Same real-shot accounting split by the rack in force at fire time, so a
     # later data-driven pass can rank guns per mode (1v1 vs melee).
-    gunRealShotsByMode: array[vb.RackMode, array[17, int]]
-    gunRealHitsByMode:  array[vb.RackMode, array[17, int]]
+    # These four arrays and `gunSelectionCount` are indexed by SELECTED GUN ID,
+    # so their width is `NumRackGuns`, not a literal. A literal `array[17, int]`
+    # survived the addition of rack id 17 (BITBRAIN) and indexed one past the end
+    # on the first tick that gun was selected — an IndexDefect in a debug build
+    # and silent corruption of the adjacent `lastPowerLogKey` string in the
+    # shipped `-d:release` binary, i.e. a bot that aims, moves and never fires.
+    gunRealShotsByMode: array[vb.RackMode, array[NumRackGuns, int]]
+    gunRealHitsByMode:  array[vb.RackMode, array[NumRackGuns, int]]
     pendingFires: seq[PendingShot]  ## FIFO of fired shots awaiting onBulletFired bulletId stamp
     bulletGun:    Table[int, int]  ## bulletId -> gun id, filled on onBulletFired, drained on resolution
     bulletMode:   Table[int, vb.RackMode]  ## bulletId -> rack at fire time
     bulletShot:   Table[int, PendingShot]  ## bulletId -> shot metadata (Task A shot log)
     pendingHitBullets: HashSet[int]  ## hit bulletIds seen before their onBulletFired stamp
-    gunSelectionCount: array[17, int]
+    gunSelectionCount: array[NumRackGuns, int]
     lastPowerLogKey: string  ## change detector for the TR_POWER_LOG line
     lastKnownTargetId: int  ## persists through death, used for round-end stats
     # Radar measurement instrumentation (only touched when RadarScanLog is set).
@@ -790,7 +796,7 @@ method onRoundEnded*(bot: ModularBot, e: RoundEndedEventForBot) =
   let fit = bot.tracker.fitnessFor(targetId)
 
   var gunsArr = newJArray()
-  for gid in 0..<17:
+  for gid in 0..<NumRackGuns:
     var totalShots = 0
     var totalHits  = 0
     for binIdx in 0..<len(vb.PowerBins):
@@ -911,12 +917,12 @@ method onRoundStarted*(bot: ModularBot, e: RoundStartedEvent) =
     bot.radarAcquireTicks = 0
     bot.radarTrackTicks = 0
     bot.radarMeleeActive = false
-  for i in 0..<17:
+  for i in 0..<NumRackGuns:
     bot.gunSelectionCount[i] = 0
     bot.gunRealShots[i] = 0
     bot.gunRealHits[i] = 0
   for m in vb.RackMode:
-    for i in 0..<17:
+    for i in 0..<NumRackGuns:
       bot.gunRealShotsByMode[m][i] = 0
       bot.gunRealHitsByMode[m][i] = 0
   # Reset per-round integrity counters so each /tmp/gun_stats.jsonl line reports
@@ -1304,8 +1310,8 @@ method run*(bot: ModularBot) =
       # owning gun's onResult, so attribution survives a mid-round rack change.
       # TMPATTERN and TMHORIZON keep their own admission gate even when the knob
       # is 0, so TR_VBULLET_ADMIT_ONLY=0 reproduces the exact pre-change rack.
-      var admit: array[18, bool]
-      for gi in 0..<18:
+      var admit: array[NumRackGuns, bool]
+      for gi in 0..<NumRackGuns:
         admit[gi] = ModuleVBullets and
                     vBulletAdmitted(gi, bot.rackMode, ActiveRackMembership,
                                     VBulletAdmitOnly or gi == TmPatternId or
@@ -1534,7 +1540,7 @@ proc seedSelectorRng() =
 
 when isMainModule:
   var bot = ModularBot(
-    tracker:    vb.initTracker(18),  # 0: HeadOn, 1: Linear, 2: Tsetlin, 3: Circular, 4: GuessFactor, 5: Pattern, 6: WallBounce, 7: Accel, 8: StopShot, 9: Displace, 10: AvgLead, 11: DecayGF, 12: KNN, 13: TMSelect, 14: TMPattern, 15: TMHorizon, 16: LeadGain, 17: BitBrainNet
+    tracker:    vb.initTracker(NumRackGuns),  # 0: HeadOn, 1: Linear, 2: Tsetlin, 3: Circular, 4: GuessFactor, 5: Pattern, 6: WallBounce, 7: Accel, 8: StopShot, 9: Displace, 10: AvgLead, 11: DecayGF, 12: KNN, 13: TMSelect, 14: TMPattern, 15: TMHorizon, 16: LeadGain, 17: BitBrainNet
     headOn:     HeadOnGun(),
     linear:     LinearGun(),
     circular:   CircularGun(),