Revert to Safari as default WebDriver browser

Chrome headless has too many issues:
- Session creation hangs when Chrome is already running
- Cloudflare and other bot protection blocks headless browsers
- Version mismatch issues between Chrome and ChromeDriver

Safari is more reliable for web automation on macOS.
Chrome headless is still available via --chrome-headless flag.

crates/g3-cli/src/lib.rs

@@ -343,11 +343,11 @@ pub struct Cli {
     #[arg(long)]
     pub webdriver: bool,
 
-    /// Use Chrome in headless mode for WebDriver (this is the default)
+    /// Use Chrome in headless mode for WebDriver (instead of Safari)
     #[arg(long)]
     pub chrome_headless: bool,
 
-    /// Use Safari for WebDriver (instead of headless Chrome)
+    /// Use Safari for WebDriver (this is the default)
     #[arg(long)]
     pub safari: bool,