fix(PPO_Bot): radar oscillation, Adam persistence, checkpoint order, channel race

- enemy_tracker: toggle lastOvershootDir each tick; make getRadarTurnRate take var tracker
- training: remove threadvar Adam globals; pass adamStates as var param to ppoUpdate; export ACAdamStates
- PPO_Bot: carry ACAdamStates through TrainingArgs/TrainingResult; drop trainingDone bool and Lock — use resultChan.tryRecv() directly as synchronisation
- weights: sort checkpoint dirs newest-first by mtime instead of hardcoded order
- tests/test_training: pass explicit ACAdamStates to ppoUpdate

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

PPO_Bot/PPO_Bot.nim

@@ -1,7 +1,7 @@
 ## PPO_Bot — enemy tracker + state vector wired into the game loop.
 ## Training: trajectory collected per tick, PPO update in background thread.
 
-import std/[os, locks]
+import std/os
 import arraymancer
 import tankroyale_botapi
 import network
@@ -26,30 +26,35 @@ type PPOBot = ref object of Bot
   hasLastTrans: bool
 
 var ac = initActorCritic()
+var gAdamStates: ACAdamStates  # persists across rounds
 
 # ── Background training state ─────────────────────────────────────────────────
 
-type TrainingArgs = object
-  ac:          ActorCritic
-  buffer:      TrajectoryBuffer
-  lastValue:   float32
-  roundNum:    int
-  weightsRoot: string
+type
+  TrainingResult = object
+    ac:         ActorCritic
+    adamStates: ACAdamStates
+
+  TrainingArgs = object
+    ac:          ActorCritic
+    adamStates:  ACAdamStates
+    buffer:      TrajectoryBuffer
+    lastValue:   float32
+    roundNum:    int
+    weightsRoot: string
 
 var
-  trainingThread: Thread[TrainingArgs]
-  trainingDone:   bool = true    # true = no training running / last run finished
-  trainingLock:   Lock
-  resultChan:     Channel[ActorCritic]
-  roundCounter:   int = 0
+  trainingThread:   Thread[TrainingArgs]
+  resultChan:       Channel[TrainingResult]
+  threadLaunched:   bool = false  # true while training thread is running
+  roundCounter:     int = 0
 
 proc trainingThreadProc(args: TrainingArgs) {.thread.} =
   var localAc = args.ac
-  ppoUpdate(localAc, args.buffer, lastValue = args.lastValue)
+  var localAdam = args.adamStates
+  ppoUpdate(localAc, args.buffer, lastValue = args.lastValue, adamStates = localAdam)
   saveCheckpoint(localAc, args.weightsRoot, args.roundNum)
-  resultChan.send(localAc)
-  withLock(trainingLock):
-    trainingDone = true
+  resultChan.send(TrainingResult(ac: localAc, adamStates: localAdam))
 
 # ── Bot methods ───────────────────────────────────────────────────────────────
 
@@ -71,12 +76,13 @@ method onRoundEnded*(bot: PPOBot, e: RoundEndedEventForBot) =
   if bot.hasLastTrans and bot.buffer.len > 0:
     bot.buffer.transitions[^1].reward += roundReward
 
-  # Pick up result from previous training thread if done
-  withLock(trainingLock):
-    if trainingDone and roundCounter > 1:
-      let (avail, trained) = resultChan.tryRecv()
-      if avail:
-        ac = trained
+  # Pick up result from previous training thread if available; channel IS the sync
+  if threadLaunched:
+    let (avail, trained) = resultChan.tryRecv()
+    if avail:
+      ac = trained.ac
+      gAdamStates = trained.adamStates
+      threadLaunched = false
 
   if bot.buffer.len == 0:
     bot.hasLastTrans = false
@@ -84,15 +90,14 @@ method onRoundEnded*(bot: PPOBot, e: RoundEndedEventForBot) =
 
   # If last thread still running, drop this pass — start fresh with newer data
   # ponytail: simple drop; queue if every round must train
-  withLock(trainingLock):
-    if not trainingDone:
-      bot.buffer.clear()
-      bot.hasLastTrans = false
-      return
-    trainingDone = false
+  if threadLaunched:
+    bot.buffer.clear()
+    bot.hasLastTrans = false
+    return
 
   let args = TrainingArgs(
     ac:          ac,
+    adamStates:  gAdamStates,
     buffer:      bot.buffer,
     lastValue:   0.0'f32,
     roundNum:    roundCounter,
@@ -102,6 +107,7 @@ method onRoundEnded*(bot: PPOBot, e: RoundEndedEventForBot) =
   bot.hasLastTrans = false
 
   createThread(trainingThread, trainingThreadProc, args)
+  threadLaunched = true
 
 method run(bot: PPOBot) =
   # Seed energy on first tick
@@ -166,7 +172,6 @@ method run(bot: PPOBot) =
     go()
 
 when isMainModule:
-  initLock(trainingLock)
   resultChan.open()
   createDir(weightsRoot)
   cleanStaleTempDirs(weightsRoot)