feature: add stealth mode, launch args, and init scripts to BrowserOptions

Add anti-bot-detection evasion support to reduce blocking by sites like
archive.ph. Stealth mode is enabled by default for all browsers and applies
common evasions: navigator.webdriver override, plugin/mimeType spoofing,
window.chrome stub, and outerWidth/outerHeight fixes. For Chromium,
--disable-blink-features=AutomationControlled is also added.

New BrowserOptions fields:
- Stealth *bool: toggle stealth presets (default true)
- LaunchArgs []string: custom browser launch arguments
- InitScripts []string: JavaScript injected before page scripts

Closes #56

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

playwright.go

@@ -70,6 +70,20 @@ type BrowserOptions struct {
 
 	// UseLocalOnly will, if set, not connect to the Playwright server, and instead launch a local browser.
 	UseLocalOnly bool
+
+	// LaunchArgs are additional command-line arguments passed to the browser process.
+	// For example: []string{"--disable-blink-features=AutomationControlled"}
+	LaunchArgs []string
+
+	// InitScripts are JavaScript snippets injected into every new browser context
+	// before any page scripts run. Useful for overriding detectable properties like
+	// navigator.webdriver.
+	InitScripts []string
+
+	// Stealth enables anti-bot-detection measures. When non-nil and true, common
+	// evasions are applied automatically (launch args + init scripts). When nil,
+	// defaults to true in NewBrowser / NewInteractiveBrowser.
+	Stealth *bool
 }
 
 func sameSiteToPlaywright(s SameSite) *playwright.SameSiteAttribute {
@@ -134,6 +148,7 @@ func NewBrowser(ctx context.Context, opts ...BrowserOptions) (Browser, error) {
 		UserAgent: DefaultUserAgent,
 		Browser:   BrowserFirefox,
 		Timeout:   &thirtySeconds,
+		Stealth:   Bool(true),
 	}, opts)
 
 	if err := ctx.Err(); err != nil {