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>

cmd/browser/pkg/browser/flags.go

@@ -41,6 +41,11 @@ var Flags = BrowserFlags{
 		Usage:       "If set, the browser will be visible, if not set, the browser will be headless",
 		DefaultText: "false",
 	},
+	&cli.BoolFlag{
+		Name:        "no-stealth",
+		Usage:       "Disable stealth mode (anti-bot-detection evasions are enabled by default)",
+		DefaultText: "false",
+	},
 }
 
 func FromCommand(ctx context.Context, cmd *cli.Command) (extractor.Browser, error) {
@@ -74,5 +79,9 @@ func FromCommand(ctx context.Context, cmd *cli.Command) (extractor.Browser, erro
 		opts.ShowBrowser = extractor.Bool(cmd.Bool("visible"))
 	}
 
+	if cmd.IsSet("no-stealth") && cmd.Bool("no-stealth") {
+		opts.Stealth = extractor.Bool(false)
+	}
+
 	return extractor.NewBrowser(ctx, opts)
 }