feat: add shared integration test framework for garages (#126)

Implements:
- BattleResult type and JSON-lines parser (#127)
- TR server lifecycle manager (#128)
- Bot compiler using nim c (#129)
- runBattle() orchestrator (#130)
- Example test in OscillatorBot_garage (#131)
- Framework usage guide (#132)
- TestBattleRunner.java for external server (#133)
- BattleRunner process lifecycle (#134)

Fix: runner_process.nim was redefining TimeoutError locally; now
uses std/net.TimeoutError consistently with server_manager.nim.

tools/battle_runner/run_test_battle.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+JAR="${TANK_ROYALE_JAR:-/home/davide/Projects/tank-royale/runner/examples/lib/robocode-tankroyale-runner.jar}"
+
+cd "$SCRIPT_DIR"
+
+if [ ! -f TestBattleRunner.class ] || [ TestBattleRunner.java -nt TestBattleRunner.class ]; then
+    echo ">>> Compiling TestBattleRunner.java..." >&2
+    javac -cp "$JAR" TestBattleRunner.java
+fi
+
+exec java -cp ".:$JAR" TestBattleRunner "$@"