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>

cmd/browser/pkg/browser/flags.go

@@ -44,7 +44,7 @@ var Flags = BrowserFlags{
 }
 
 func FromCommand(ctx context.Context, cmd *cli.Command) (extractor.Browser, error) {
-	var opts extractor.PlayWrightBrowserOptions
+	var opts extractor.BrowserOptions
 
 	if ua := cmd.String("user-agent"); ua != "" {
 		opts.UserAgent = ua
@@ -59,7 +59,7 @@ func FromCommand(ctx context.Context, cmd *cli.Command) (extractor.Browser, erro
 	}
 
 	if b := cmd.String("browser"); b != "" {
-		opts.Browser = extractor.PlayWrightBrowserSelection(b)
+		opts.Browser = extractor.BrowserSelection(b)
 	}
 
 	if cf := cmd.String("cookies-file"); cf != "" {
@@ -72,5 +72,5 @@ func FromCommand(ctx context.Context, cmd *cli.Command) (extractor.Browser, erro
 
 	opts.ShowBrowser = cmd.Bool("visible")
 
-	return extractor.NewPlayWrightBrowser(ctx, opts)
+	return extractor.NewBrowser(ctx, opts)
 }