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/megamillions/megamillions.go

@@ -3,7 +3,6 @@ package megamillions
 import (
 	"context"
 	"fmt"
-	"io"
 	"strconv"
 	"strings"
 	"time"
@@ -33,12 +32,6 @@ type NextDrawing struct {
 	Jackpot currency.Amount
 }
 
-func deferClose(cl io.Closer) {
-	if cl != nil {
-		_ = cl.Close()
-	}
-}
-
 func netTicksToTime(t int64) time.Time {
 	return time.Unix(0, t*100).Add(-621355968000000000)
 }
@@ -218,7 +211,7 @@ func (c Config) GetCurrent(ctx context.Context, b extractor.Browser) (*Drawing,
 		return nil, nil, err
 	}
 
-	defer deferClose(doc)
+	defer extractor.DeferClose(doc)
 
 	d, err := getDrawing(ctx, doc)