Plan: Add External JS Minification Tool Support

     1. Configuration Structure

     Add a new [tools] section to the page config to specify external minification tools:
     [tools]
     # External minification tools (optional)
     js_minifier = "terser"  # terser, uglifyjs, esbuild, swc, or path to custom tool
     js_minifier_path = "/usr/local/bin/terser"  # Optional: explicit path
     js_minifier_args = ["--compress", "--mangle"]  # Optional: custom arguments
     css_minifier = ""  # Future: similar for CSS
     html_minifier = ""  # Future: similar for HTML

     2. Framework Changes

     A. Update framework/templates/page.config.toml.template

     - Add the [tools] section with sensible defaults
     - Document available minifiers and their options

     B. Update framework/core/framework-utils.nu

     - Add tool configuration extraction from page config
     - Handle optional tool paths and arguments

     C. Enhance framework/optimizers/optimize-js.nu

     - Add minify_js_with_tool function that:
       - Checks if external tool is configured
       - Validates tool availability
       - Falls back to built-in minification if tool not found
       - Handles tool execution with proper error handling

     D. Update framework/core/build.nu

     - Modify the JS build process to check for external tools
     - Use external tool for production/staging builds
     - Keep built-in minification for development or as fallback

     3. Tool Detection & Fallback Strategy

     # Pseudo-code for tool selection
     if $config.tools.js_minifier and not $dev {
         if (check_tool_available $config.tools.js_minifier) {
             use external_minifier
         } else {
             print warning "Tool not found, using built-in minifier"
             use built_in_minifier
         }
     } else {
         use built_in_minifier
     }

     4. Supported Tools

     Initially support these popular JS minifiers:
     - terser - Modern JS minifier (npm install -g terser)
     - uglifyjs - Classic JS minifier (npm install -g uglify-js)
     - esbuild - Fast bundler/minifier (npm install -g esbuild)
     - swc - Rust-based fast minifier (npm install -g @swc/cli @swc/core)

     5. Example Usage

     Pages that need advanced JS minification can configure:
     [tools]
     js_minifier = "terser"
     js_minifier_args = ["--compress", "drop_console=true", "--mangle", "--toplevel"]

     6. Benefits

     - Professional-grade minification for production
     - Configurable per page or globally
     - Graceful fallback to built-in minifier
     - Support for different tools based on project needs
     - Future extensibility for CSS and HTML tools