refactor: restructure API, deduplicate code, expand test coverage

- Extract shared DeferClose helper, removing 14 duplicate copies
- Rename PlayWright-prefixed types to cleaner names (BrowserOptions,
  BrowserSelection, NewBrowser, etc.)
- Rename fields: ServerAddress, RequireServer (was DontLaunchOnConnectFailure)
- Extract shared initBrowser/mergeOptions into browser_init.go,
  deduplicating ~120 lines between NewBrowser and NewInteractiveBrowser
- Remove unused locator field from document struct
- Add tests for all previously untested packages (archive, aislegopher,
  wegmans, useragents, powerball) and expand existing test suites
- Add MIGRATION.md documenting all breaking API changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sites/powerball/powerball_test.go

@@ -0,0 +1,34 @@
+package powerball
+
+import "testing"
+
+func TestConfig_Validate(t *testing.T) {
+	c := Config{}
+	c = c.validate()
+	// validate is a no-op for powerball Config, just verify it doesn't panic.
+	_ = c
+}
+
+func TestDefaultConfig(t *testing.T) {
+	c := DefaultConfig
+	_ = c
+}
+
+func TestDrawing_ZeroValue(t *testing.T) {
+	var d Drawing
+	if d.PowerBall != 0 || d.PowerPlay != 0 {
+		t.Error("zero-value Drawing should have zero fields")
+	}
+	for i, n := range d.Numbers {
+		if n != 0 {
+			t.Errorf("Numbers[%d] = %d, want 0", i, n)
+		}
+	}
+}
+
+func TestNextDrawing_ZeroValue(t *testing.T) {
+	var nd NextDrawing
+	if nd.Date != "" || nd.JackpotDollars != 0 {
+		t.Error("zero-value NextDrawing should have empty/zero fields")
+	}
+}