Add AGENTS.md and Ember Best Practices skill

.agents/skills/ember-best-practices/rules/bundle-direct-imports.md

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+---
+title: Avoid Importing Entire Addon Namespaces
+impact: CRITICAL
+impactDescription: 200-500ms import cost reduction
+tags: bundle, imports, tree-shaking, performance
+---
+
+## Avoid Importing Entire Addon Namespaces
+
+Import specific utilities and components directly rather than entire addon namespaces to enable better tree-shaking and reduce bundle size.
+
+**Incorrect (imports entire namespace):**
+
+```javascript
+import { tracked } from '@glimmer/tracking';
+import Component from '@glimmer/component';
+import { action } from '@ember/object';
+// OK - these are already optimized
+
+// But avoid this pattern with utility libraries:
+import * as lodash from 'lodash';
+import * as moment from 'moment';
+
+class My extends Component {
+  someMethod() {
+    return lodash.debounce(this.handler, 300);
+  }
+}
+```
+
+**Correct (direct imports):**
+
+```javascript
+import { tracked } from '@glimmer/tracking';
+import Component from '@glimmer/component';
+import { action } from '@ember/object';
+import debounce from 'lodash/debounce';
+import dayjs from 'dayjs'; // moment alternative, smaller
+
+class My extends Component {
+  someMethod() {
+    return debounce(this.handler, 300);
+  }
+}
+```
+
+**Even better (use Ember utilities when available):**
+
+```javascript
+import { tracked } from '@glimmer/tracking';
+import Component from '@glimmer/component';
+import { action } from '@ember/object';
+import { debounce } from '@ember/runloop';
+
+class My extends Component {
+  someMethod() {
+    return debounce(this, this.handler, 300);
+  }
+}
+```
+
+Direct imports and using built-in Ember utilities reduce bundle size by avoiding unused code.