Fix site_id isolation for demo sites

- Auto-derive site_id from demo directory paths (demos/demo-site -> 'demo', demos/simple/test-simple -> 'simple')
- Add validation requiring explicit site_id for non-demo paths with helpful error messages
- Remove JavaScript 'demo' fallback and add proper error messaging for missing site_id
- Ensure each demo site uses isolated content namespace to prevent content mixing

Resolves issue where /sites/simple and /sites/demo both used site_id=demo

cmd/enhance.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"strings"
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
@@ -49,6 +50,30 @@ func runEnhance(cmd *cobra.Command, args []string) {
 	siteID := viper.GetString("cli.site_id")
 	outputDir := viper.GetString("cli.output")
 
+	// Auto-derive site_id for demo paths or validate for production
+	if strings.Contains(inputDir, "/demos/") {
+		// Auto-derive site_id from demo path
+		siteID = content.DeriveOrValidateSiteID(inputDir, siteID)
+	} else {
+		// Validate site_id for non-demo paths
+		if siteID == "" || siteID == "demo" {
+			log.Fatalf(`❌ site_id must be explicitly configured for non-demo sites.
+
+💡 Examples:
+   # Set via command line:
+   insertr enhance --site-id mysite /path/to/site
+
+   # Set in insertr.yaml:
+   cli:
+     site_id: "mysite"
+
+   # Set via environment:
+   INSERTR_CLI_SITE_ID=mysite insertr enhance /path/to/site
+
+🚀 For demo sites under demos/, site_id is auto-derived from the directory name.`)
+		}
+	}
+
 	// Create content client
 	var client engine.ContentClient
 	if apiURL != "" {

internal/content/enhancer.go

@@ -194,13 +194,89 @@ func (e *Enhancer) enhanceWithEngine(htmlContent []byte, filePath string) ([]byt
 
 // EnhanceInPlace performs in-place enhancement of static site files
 func (e *Enhancer) EnhanceInPlace(sitePath string, siteID string) error {
-	// Update the enhancer's site ID for this operation
+	// Use the provided siteID (derivation should happen at CLI level)
 	e.siteID = siteID
 
 	// Use EnhanceDirectory with same input and output (in-place)
 	return e.EnhanceDirectory(sitePath, sitePath)
 }
 
+// DeriveOrValidateSiteID automatically derives site_id for demo paths or validates for production
+func DeriveOrValidateSiteID(sitePath string, configSiteID string) string {
+	// Check if this is a demo path
+	if strings.Contains(sitePath, "/demos/") {
+		return deriveDemoSiteID(sitePath)
+	}
+
+	// For non-demo paths, return the configured site_id
+	// Validation of non-demo site_id will be handled at the CLI level
+	return configSiteID
+}
+
+// deriveDemoSiteID extracts site_id from demo directory structure
+func deriveDemoSiteID(sitePath string) string {
+	// Convert to absolute path and clean it
+	absPath, err := filepath.Abs(sitePath)
+	if err != nil {
+		absPath = sitePath
+	}
+	absPath = filepath.Clean(absPath)
+
+	// Look for patterns in demo paths:
+	// demos/demo-site_enhanced -> "demo"
+	// demos/simple/test-simple_enhanced -> "simple"
+	// demos/simple/dan-eden-portfolio -> "dan-eden"
+
+	parts := strings.Split(absPath, string(filepath.Separator))
+
+	// Find the demos directory index
+	demosIndex := -1
+	for i, part := range parts {
+		if part == "demos" {
+			demosIndex = i
+			break
+		}
+	}
+
+	if demosIndex == -1 || demosIndex >= len(parts)-1 {
+		// Fallback if demos not found in path
+		return "demo"
+	}
+
+	// Get the segment after demos/
+	nextSegment := parts[demosIndex+1]
+
+	// Handle different demo directory patterns:
+	if strings.HasPrefix(nextSegment, "demo-site") {
+		return "demo"
+	}
+
+	if nextSegment == "simple" && len(parts) > demosIndex+2 {
+		// For demos/simple/something, use the something part
+		finalSegment := parts[demosIndex+2]
+
+		// Extract meaningful name from directory
+		if strings.HasPrefix(finalSegment, "test-") {
+			// test-simple_enhanced -> simple
+			return "simple"
+		}
+		if strings.Contains(finalSegment, "dan-eden") {
+			return "dan-eden"
+		}
+
+		// Generic case: use the directory name as-is
+		return strings.TrimSuffix(finalSegment, "_enhanced")
+	}
+
+	// Default case: use the immediate subdirectory of demos/
+	result := strings.TrimSuffix(nextSegment, "_enhanced")
+
+	// Clean up common suffixes
+	result = strings.TrimSuffix(result, "-site")
+
+	return result
+}
+
 // copyFile copies a file from src to dst
 func (e *Enhancer) copyFile(src, dst string) error {
 	// Create directory for destination

lib/src/core/api-client.js

@@ -10,7 +10,7 @@ export class ApiClient {
             : '/api/content';                      // Production: same-origin API
             
         this.baseUrl = options.apiEndpoint || defaultEndpoint;
-        this.siteId = options.siteId || 'demo';
+        this.siteId = options.siteId || this.handleMissingSiteId();
         
         // Log API configuration in development
         if (isDevelopment && !options.apiEndpoint) {
@@ -276,6 +276,22 @@ export class ApiClient {
         return false;
     }
     
+    /**
+     * Handle missing site_id configuration
+     * @returns {string} Site ID or throws error
+     */
+    handleMissingSiteId() {
+        console.error('❌ No site_id configured for Insertr.');
+        console.log('💡 Add data-site-id attribute to your script tag:');
+        console.log('   <script src="insertr.js" data-site-id="mysite"></script>');
+        console.log('');
+        console.log('🚀 For demos under demos/, site_id is auto-derived from directory name.');
+        console.log('🏭 For production sites, you must explicitly set your site_id.');
+        
+        // Return a placeholder that will cause API calls to fail gracefully
+        return '__MISSING_SITE_ID__';
+    }
+
     /**
      * Get current file path from URL for consistent ID generation
      * @returns {string} File path like "index.html", "about.html"

lib/src/index.js

@@ -84,7 +84,7 @@ function autoInitialize() {
         const config = {};
         
         if (insertrScript) {
-            config.siteId = insertrScript.getAttribute('data-site-id') || 'demo';
+            config.siteId = insertrScript.getAttribute('data-site-id'); // No fallback - let ApiClient handle missing values
             config.apiEndpoint = insertrScript.getAttribute('data-api-endpoint') || '/api/content';
             config.mockAuth = insertrScript.getAttribute('data-mock-auth') === 'true';
             config.debug = insertrScript.getAttribute('data-debug') === 'true';