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/wegmans/cmd/wegmans/main.go

@@ -3,10 +3,10 @@ package main
 import (
 	"context"
 	"fmt"
-	"io"
 	"net/url"
 	"os"
 
+	"gitea.stevedudenhoeffer.com/steve/go-extractor"
 	"gitea.stevedudenhoeffer.com/steve/go-extractor/cmd/browser/pkg/browser"
 
 	"github.com/urfave/cli/v3"
@@ -14,12 +14,6 @@ import (
 	"gitea.stevedudenhoeffer.com/steve/go-extractor/sites/wegmans"
 )
 
-func deferClose(cl io.Closer) {
-	if cl != nil {
-		_ = cl.Close()
-	}
-}
-
 type WegmansFlags []cli.Flag
 
 var Flags = WegmansFlags{}
@@ -44,7 +38,7 @@ func main() {
 			cfg := Flags.ToConfig(cmd)
 
 			b, err := browser.FromCommand(ctx, cmd)
-			defer deferClose(b)
+			defer extractor.DeferClose(b)
 
 			if err != nil {
 				return fmt.Errorf("error creating browser: %w", err)

sites/wegmans/wegmans.go

@@ -3,7 +3,6 @@ package wegmans
 import (
 	"context"
 	"errors"
-	"io"
 	"log/slog"
 	"net/url"
 	"strconv"
@@ -30,12 +29,6 @@ type Item struct {
 	Unit      string
 }
 
-func deferClose(c io.Closer) {
-	if c != nil {
-		_ = c.Close()
-	}
-}
-
 func (c Config) GetItemPrice(ctx context.Context, b extractor.Browser, u *url.URL) (Item, error) {
 
 	if b == nil {
@@ -68,7 +61,7 @@ func (c Config) GetItemPrice(ctx context.Context, b extractor.Browser, u *url.UR
 	}
 
 	doc, err := b.Open(ctx, u.String(), extractor.OpenPageOptions{})
-	defer deferClose(doc)
+	defer extractor.DeferClose(doc)
 
 	if err != nil {
 		return Item{}, err

sites/wegmans/wegmans_test.go

@@ -0,0 +1,39 @@
+package wegmans
+
+import (
+	"context"
+	"net/url"
+	"testing"
+)
+
+func TestGetItemPrice_NilBrowser(t *testing.T) {
+	u, _ := url.Parse("https://shop.wegmans.com/product/24921")
+	_, err := DefaultConfig.GetItemPrice(context.Background(), nil, u)
+	if err != ErrNilBrowser {
+		t.Errorf("expected ErrNilBrowser, got %v", err)
+	}
+}
+
+func TestGetItemPrice_NilURL(t *testing.T) {
+	// NilBrowser check comes before NilURL, so we can't test NilURL
+	// independently without a real browser. Verify the error sentinel exists.
+	if ErrNilURL.Error() != "url is nil" {
+		t.Errorf("ErrNilURL = %q, want %q", ErrNilURL.Error(), "url is nil")
+	}
+}
+
+func TestGetItemPrice_ErrorSentinels(t *testing.T) {
+	if ErrInvalidURL.Error() != "invalid url" {
+		t.Errorf("ErrInvalidURL = %q, want %q", ErrInvalidURL.Error(), "invalid url")
+	}
+	if ErrNilBrowser.Error() != "browser is nil" {
+		t.Errorf("ErrNilBrowser = %q, want %q", ErrNilBrowser.Error(), "browser is nil")
+	}
+}
+
+func TestItem_ZeroValue(t *testing.T) {
+	var item Item
+	if item.ID != 0 || item.Name != "" || item.Price != 0 || item.UnitPrice != 0 || item.Unit != "" {
+		t.Error("zero-value Item should have empty/zero fields")
+	}
+}