Make WebDriver and Chrome headless enabled by default

- webdriver flag now defaults to true (tools always available)
- chrome_headless flag now defaults to true (Chrome is default browser)
- Use --safari flag to override and use Safari instead
- Updated README documentation to reflect new defaults

crates/g3-cli/src/cli_args.rs

@@ -68,14 +68,14 @@ pub struct Cli {
     pub quiet: bool,
 
     /// Enable WebDriver browser automation tools
-    #[arg(long)]
+    #[arg(long, default_value_t = true)]
     pub webdriver: bool,
 
     /// Use Chrome in headless mode for WebDriver (instead of Safari)
-    #[arg(long)]
+    #[arg(long, default_value_t = true)]
     pub chrome_headless: bool,
 
-    /// Use Safari for WebDriver (this is the default)
+    /// Use Safari for WebDriver (overrides the default Chrome headless)
     #[arg(long)]
     pub safari: bool,