Fix code quality violations and exclude Manifest from checks

Document application modes (development/debug/production)
Add global file drop handler, order column normalization, SPA hash fix
Serve CDN assets via /_vendor/ URLs instead of merging into bundles
Add production minification with license preservation
Improve JSON formatting for debugging and production optimization
Add CDN asset caching with CSS URL inlining for production builds
Add three-mode system (development, debug, production)
Update Manifest CLAUDE.md to reflect helper class architecture
Refactor Manifest.php into helper classes for better organization
Pre-manifest-refactor checkpoint: Add app_mode documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

node_modules/csso/cjs/clean/Atrule.cjs

@@ -0,0 +1,73 @@
+'use strict';
+
+const cssTree = require('css-tree');
+const utils = require('./utils.cjs');
+
+function cleanAtrule(node, item, list) {
+    if (node.block) {
+        // otherwise removed at-rule don't prevent @import for removal
+        if (this.stylesheet !== null) {
+            this.stylesheet.firstAtrulesAllowed = false;
+        }
+
+        if (utils.hasNoChildren(node.block)) {
+            list.remove(item);
+            return;
+        }
+    }
+
+    switch (node.name) {
+        case 'charset':
+            if (utils.hasNoChildren(node.prelude)) {
+                list.remove(item);
+                return;
+            }
+
+            // if there is any rule before @charset -> remove it
+            if (item.prev) {
+                list.remove(item);
+                return;
+            }
+
+            break;
+
+        case 'import':
+            if (this.stylesheet === null || !this.stylesheet.firstAtrulesAllowed) {
+                list.remove(item);
+                return;
+            }
+
+            // if there are some rules that not an @import or @charset before @import
+            // remove it
+            list.prevUntil(item.prev, function(rule) {
+                if (rule.type === 'Atrule') {
+                    if (rule.name === 'import' || rule.name === 'charset') {
+                        return;
+                    }
+                }
+
+                this.root.firstAtrulesAllowed = false;
+                list.remove(item);
+
+                return true;
+            }, this);
+
+            break;
+
+        default: {
+            const name = cssTree.keyword(node.name).basename;
+
+            if (name === 'keyframes' ||
+                name === 'media' ||
+                name === 'supports') {
+
+                // drop at-rule with no prelude
+                if (utils.hasNoChildren(node.prelude) || utils.hasNoChildren(node.block)) {
+                    list.remove(item);
+                }
+            }
+        }
+    }
+}
+
+module.exports = cleanAtrule;