fix(ui): use lit/directives instead of lit-html/directives for ifDefined

The ifDefined import from 'lit-html/directives/if-defined.js' resolved to
lit-html@1.4.1 (via pnpm root node_modules), but LitElement's render()
uses lit@2.8.0's template engine. The 2.x renderer doesn't recognize 1.x
directive functions (different branding: WeakMap vs _$litDirective$
property), so it stringified the function — causing minified JS code to
appear as placeholder text in j-input and other components.

Fix: import from 'lit/directives/if-defined.js' which always resolves to
the lit-html version bundled with lit@2.8.0.

Author: HexaField

packages/ui/lib/components/input/Input.js

@@ -1,5 +1,5 @@
 import { LitElement, html, css } from 'lit';
-import { ifDefined } from 'lit-html/directives/if-defined.js';
+import { ifDefined } from 'lit/directives/if-defined.js';
 import sharedStyles from '../../shared/styles';
 
 const styles = css`

packages/ui/lib/components/tab-item/TabItem.ts

@@ -1,6 +1,6 @@
 import { LitElement, html, css } from 'lit';
 import { state, customElement, property } from 'lit/decorators.js';
-import { ifDefined } from 'lit-html/directives/if-defined.js';
+import { ifDefined } from 'lit/directives/if-defined.js';
 import sharedStyles from '../../shared/styles';
 
 const styles = css`