feat: add unlock system with 3 unlockable contents

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

store/unlocks_test.go

@@ -0,0 +1,47 @@
+package store
+
+import (
+	"testing"
+)
+
+func TestUnlockContent(t *testing.T) {
+	dir := t.TempDir()
+	db, err := Open(dir + "/test_unlocks.db")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	// Initially not unlocked
+	if db.IsUnlocked("fp1", "fifth_class") {
+		t.Error("should not be unlocked initially")
+	}
+
+	// Unlock returns true for new unlock
+	newlyUnlocked, err := db.UnlockContent("fp1", "fifth_class")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !newlyUnlocked {
+		t.Error("should be newly unlocked")
+	}
+
+	// Now it should be unlocked
+	if !db.IsUnlocked("fp1", "fifth_class") {
+		t.Error("should be unlocked after UnlockContent")
+	}
+
+	// Second unlock returns false (already unlocked)
+	newlyUnlocked2, err := db.UnlockContent("fp1", "fifth_class")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if newlyUnlocked2 {
+		t.Error("should not be newly unlocked on second call")
+	}
+
+	// Different player still not unlocked
+	if db.IsUnlocked("fp2", "fifth_class") {
+		t.Error("different player should not have unlock")
+	}
+}