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>

close_test.go

@@ -0,0 +1,38 @@
+package extractor
+
+import (
+	"errors"
+	"testing"
+)
+
+type mockCloser struct {
+	closed bool
+	err    error
+}
+
+func (m *mockCloser) Close() error {
+	m.closed = true
+	return m.err
+}
+
+func TestDeferClose_Nil(t *testing.T) {
+	// Should not panic on nil.
+	DeferClose(nil)
+}
+
+func TestDeferClose_Valid(t *testing.T) {
+	m := &mockCloser{}
+	DeferClose(m)
+	if !m.closed {
+		t.Error("DeferClose did not call Close()")
+	}
+}
+
+func TestDeferClose_ErrorIgnored(t *testing.T) {
+	m := &mockCloser{err: errors.New("close error")}
+	// Should not panic even when Close returns an error.
+	DeferClose(m)
+	if !m.closed {
+		t.Error("DeferClose did not call Close()")
+	}
+}