Replace the broken test suite with working GdUnit4 tests

The previous tests never compiled: they used GUT's assert functions,
Godot 3 APIs and reassigned autoload functions, so no test ran.

- 90 tests: unit tests for the playlist, songs, player scoring, time
  formatting, search and the server client, plus integration tests
  that run MainWindow and SyncWindow against a fake server
- Keybind tests check that Alt+<number> and Ctrl+Alt+<number> keep
  following the player rows while players are added and removed
- run_tests.sh finds Godot and runs the suite headless (~10 seconds)
- CI runs the tests before the build job in gitea-build.yaml; the
  separate test.yml used a GitHub action that does not exist
- GdUnit4 is committed instead of ignored, since the project enables
  it, and .gitea/ is no longer ignored
- Exported builds leave out tests/ and addons/gdUnit4/

run_tests.sh

@@ -1,82 +1,58 @@
-#!/bin/bash
+#!/usr/bin/env bash
+# Runs the GdUnit4 test suite headless.
+#
+# Usage: ./run_tests.sh [test path ...]
+#   ./run_tests.sh                                  all tests
+#   ./run_tests.sh res://tests/unit                 only unit tests
+#   ./run_tests.sh res://tests/unit/test_search.gd  a single suite
+#
+# Godot is taken from $GODOT, then `godot` on PATH, then the macOS app bundles.
 
-# GdUnit4 Test Runner for MusicPlayer
-# Usage: ./run_tests.sh [--headless] [--verbose]
+set -euo pipefail
+cd "$(dirname "$0")"
 
-set -e
+find_godot() {
+    if [[ -n "${GODOT:-}" ]]; then
+        echo "$GODOT"
+        return
+    fi
+    if command -v godot > /dev/null; then
+        command -v godot
+        return
+    fi
+    for app in /Applications/Godot.app /Applications/Godot_mono.app; do
+        if [[ -x "$app/Contents/MacOS/Godot" ]]; then
+            echo "$app/Contents/MacOS/Godot"
+            return
+        fi
+    done
+    echo "Godot not found. Install Godot 4.7 or set GODOT=/path/to/godot" >&2
+    exit 1
+}
 
-SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-cd "$SCRIPT_DIR"
+godot_bin="$(find_godot)"
 
-# Default flags
-HEADLESS=false
-VERBOSE=false
-
-# Parse arguments
-for arg in "$@"; do
-    case "$arg" in
-        --headless)
-            HEADLESS=true
-            ;;
-        --verbose)
-            VERBOSE=true
-            ;;
-    esac
+paths=("$@")
+if [[ ${#paths[@]} -eq 0 ]]; then
+    paths=(res://tests/unit res://tests/integration)
+fi
+test_args=()
+for path in "${paths[@]}"; do
+    test_args+=(-a "$path")
 done
 
-# Godot executable (adjust if needed)
-GODOT_EXEC="godot"
+# Builds the class cache so class_name types resolve; fast when nothing changed
+"$godot_bin" --headless --path . --import > /dev/null 2>&1
 
-# Check if Godot is available
-if ! command -v "$GODOT_EXEC" &> /dev/null; then
-    echo "Error: Godot executable not found at: $GODOT_EXEC"
-    echo "Please ensure Godot 4.7 is installed and in your PATH"
-    exit 1
+set +e
+"$godot_bin" --headless --path . \
+    -s addons/gdUnit4/bin/GdUnitCmdTool.gd --ignoreHeadlessMode "${test_args[@]}"
+exit_code=$?
+set -e
+
+# GdUnit4 exits with 101 when tests pass but report warnings (e.g. orphan nodes)
+if [[ $exit_code -eq 101 ]]; then
+    echo "Tests passed with warnings, see the report above."
+    exit 0
 fi
-
-# Build arguments
-GODOT_ARGS=(
-    "--path" "."
-    "-s" "addons/gdUnit4/test.gd"
-    "--gdunit.cli"
-)
-
-if [ "$HEADLESS" = true ]; then
-    GODOT_ARGS+=("--headless")
-fi
-
-if [ "$VERBOSE" = true ]; then
-    GODOT_ARGS+=("--verbose")
-fi
-
-echo "Running tests with Godot..."
-echo "Command: $GODOT_EXEC ${GODOT_ARGS[*]}"
-echo ""
-
-# Run tests
-"$GODOT_EXEC" "${GODOT_ARGS[@]}"
-EXIT_CODE=$?
-
-# Check results
-echo ""
-if [ $EXIT_CODE -eq 0 ]; then
-    echo "✓ All tests passed!"
-else
-    echo "✗ Tests failed with exit code: $EXIT_CODE"
-fi
-
-# Check for test results files
-if [ -f "test_results.xml" ]; then
-    echo ""
-    echo "Test results:"
-    echo "  - JUnit XML: test_results.xml"
-    echo "  - HTML: test_results.html"
-    
-    # Count failures
-    FAILURES=$(grep -c '<failure' test_results.xml || true)
-    if [ "$FAILURES" -gt 0 ]; then
-        echo "  - Failures: $FAILURES"
-    fi
-fi
-
-exit $EXIT_CODE
+exit $exit_code