fix(PPO_Bot): radar lock — use enemy_tracker width-lock, fix arctan2 arg order

Three bugs caused the radar to sweep continuously instead of locking:

1. run() loop set radar to Inf every tick, overwriting any lock
   → replaced with enemy_tracker.getRadarTurnRate()

2. onScannedBot used radarBearingTo() (math convention, east=0 CCW)
   → removed; run loop now handles radar via enemy_tracker

3. enemy_tracker.getRadarTurnRate() had arctan2(dx,dy) instead of
   arctan2(dy,dx) — introduced by fd22535; bearing was off by ~90°

Also relaxed stale-lock threshold from 2 to 8 ticks to survive
brief scan gaps without falling back to full sweep.

Added tools/battle_runner for automated 1v1 testing.

Result: 1303/1308 ticks with successful scan (was ~1 in 4).

tools/battle_runner/run.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
+
+JAR="${TANK_ROYALE_JAR:-/home/davide/Projects/tank-royale/runner/examples/lib/robocode-tankroyale-runner.jar}"
+PPO_BOT_SRC="$REPO_ROOT/PPO_Bot"
+
+export PPO_BOT_DIR="$PPO_BOT_SRC"
+export SAMPLE_BOTS_DIR="${SAMPLE_BOTS_DIR:-/home/davide/Projects/tank-royale/sample-bots/java/build/archive}"
+
+# ── 1. Compile PPO_Bot if binary is missing ──────────────────────────────────
+if [ ! -x "$PPO_BOT_SRC/PPO_Bot" ]; then
+    echo ">>> Compiling PPO_Bot..."
+    (cd "$PPO_BOT_SRC" && nimble build -d:release)
+fi
+
+# ── 2. Compile and run RunBattle.java ────────────────────────────────────────
+cd "$SCRIPT_DIR"
+
+echo ">>> Compiling RunBattle.java..."
+javac -cp "$JAR" RunBattle.java
+
+echo ">>> Running battle..."
+java -cp ".:$JAR" RunBattle