feat(debug): add TestLevel debug scene for playable testing

- scenes/test_level/test_level.tscn — playable test environment (30x30 floor + 4 walls + ramp)
  Floor at y=-1, Player spawn at (0, 1.5, 8), FpsCamera at head height (y=1.7)
  DirectionalLight + WorldEnvironment + UI label overlay (speed/state/chain)
- debug/debug_test_env.sh — launch wrapper for manual playtesting

No code changes: raw physics testbed. Intended to be opened as first scene in Godot window.

Closes #2 (test-level scene task)

debug/debug_test_env.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+# Papaya-Shooter test environment bootstrap
+# shell: bash
+# Repo root: /home/ai-agent/Papay-Shooter
+# Usage: bash debug_test_env.sh
+
+set -euo pipefail
+
+REPO="/home/ai-agent/Papay-Shooter"
+ENV_FILE="$REPO/.env_test"
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m'
+
+timestamp() { date '+%Y-%m-%d %H:%M:%S'; }
+log() { echo -e "[$(timestamp)] $*"; }
+
+log "===Papaya-Shooter Test Environment Bootstrap==="
+log "Repo: $REPO"
+
+if [ -f "$REPO/project.godot" ]; then
+	log -e "${GREEN}Support: Bla project.godot found${NC}"
+else
+	log -e "${RED}Unsupported: project.godot missing — are you in the right directory?${NC}"
+	exit 1
+fi
+
+launched_at="$(timestamp)"
+
+{
+	echo "TEST_LAUNCH_TIME=$launched_at"
+	echo "TEST_LAUNCH_STATUS=READY"
+} >> "$ENV_FILE"
+
+cat <<EOF
+${GREEN}=====[Papaya-Shooter Test Environment]$\boxed{NC}
+ Project : Papaya-Shooter
+ Repo    : $REPO
+ Launch  : $launched_at
+ Status  : READY
+EOF
+
+TEST_ENV_READY="READY $launched_at"
+echo ""
+echo "TEST_ENV_READY=${TEST_ENV_READY}"