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>

interactive.go

@@ -62,6 +62,7 @@ func NewInteractiveBrowser(ctx context.Context, opts ...BrowserOptions) (Interac
 		UserAgent: DefaultUserAgent,
 		Browser:   BrowserFirefox,
 		Timeout:   &thirtySeconds,
+		Stealth:   Bool(true),
 		Dimensions: Size{
 			Width:  1280,
 			Height: 720,