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>

mock_test.go

@@ -0,0 +1,16 @@
+package extractor
+
+import "time"
+
+// mockDocument implements the Document interface for testing without Playwright.
+type mockDocument struct {
+	mockNode
+	url     string
+	content string
+}
+
+func (m mockDocument) URL() string              { return m.url }
+func (m mockDocument) Refresh() error           { return nil }
+func (m mockDocument) Content() (string, error)  { return m.content, nil }
+func (m mockDocument) Close() error             { return nil }
+func (m mockDocument) WaitForNetworkIdle(_ *time.Duration) error { return nil }