test: add regression test suite for config/state hardening (steps 1-10)

21 tests across 6 groups:
A. Config loading & persistence (runtime path, YAML schema, overrides)
B. Runtime state (live globals reading, /config/set sync, restore)
C. Reset (full reset, single-key reset)
D. Server manager (zero-server default, corrupt handling, CRUD, no dead code)
E. GPU deduplication (delegates to config_manager, correct URL switching)
F. Clean imports (no dead os/Union/GUILD_SETTINGS)

Run: ./bot/tests/run_tests.sh (builds + runs in Docker container)

bot/tests/run_tests.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+# Run the config/state regression tests inside the miku-bot Docker container.
+#
+# Usage:
+#   ./bot/tests/run_tests.sh          # build + run
+#   ./bot/tests/run_tests.sh --no-build  # skip rebuild
+set -euo pipefail
+
+cd "$(dirname "$0")/../.."  # repo root
+
+if [[ "${1:-}" != "--no-build" ]]; then
+    echo "Building miku-bot image..."
+    docker compose build miku-bot
+fi
+
+echo ""
+echo "Running config/state regression tests..."
+echo ""
+
+docker run --rm \
+    -v "$(pwd)/config.yaml:/config.yaml:ro" \
+    -v "$(pwd)/bot/tests:/app/tests:ro" \
+    -e DISCORD_BOT_TOKEN=test_token \
+    miku-discord-miku-bot \
+    python tests/test_config_state.py