fix(widgets): stop silently discarding invalid JSON edits in the props fallback textarea

updateJson() caught JSON.parse failures and did nothing, but the textarea
was bound to propsJson(committed props) - so on the next change-detection
pass, any in-progress invalid edit snapped back to the last-saved value
with zero feedback. Verified live via window.ng.getComponent(): typing
invalid JSON now keeps the user's draft on screen with an inline error;
fixing it commits and clears the draft/error.

Also: homepage-section drop() used CdkDragDrop<any[]> - switched to
unknown[] per the no-any rule, no behavior change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/features/project-editor/sections/widgets-section.component.ts

@@ -1,4 +1,4 @@
-import { ChangeDetectionStrategy, Component, inject } from '@angular/core';
+import { ChangeDetectionStrategy, Component, inject, signal } from '@angular/core';
 import { FormsModule } from '@angular/forms';
 import { ProjectEditorFacade } from '../facade/project-editor.facade';
 import { TranslatePipe } from '../../../i18n/translate.pipe';
@@ -44,11 +44,31 @@ export class ProjectEditorWidgetsSectionComponent {
     this.updateWidget(widgetId, props => ({ ...props, [key]: value }));
   }
 
+  private readonly jsonDrafts = signal<Record<string, string>>({});
+  private readonly jsonErrors = signal<Record<string, string>>({});
+
+  /**
+   * While the textarea holds invalid JSON, keep showing the user's own draft
+   * (not the last-committed props) so their in-progress edit isn't silently
+   * overwritten on the next change-detection pass.
+   */
+  widgetJsonValue(widgetId: string, props: Record<string, unknown>): string {
+    return this.jsonDrafts()[widgetId] ?? this.propsJson(props);
+  }
+
+  widgetJsonError(widgetId: string): string | null {
+    return this.jsonErrors()[widgetId] ?? null;
+  }
+
   updateJson(widgetId: string, raw: string): void {
     try {
-      this.updateWidget(widgetId, () => JSON.parse(raw));
+      const parsed = JSON.parse(raw);
+      this.updateWidget(widgetId, () => parsed);
+      this.jsonDrafts.update(({ [widgetId]: _removed, ...rest }) => rest);
+      this.jsonErrors.update(({ [widgetId]: _removed, ...rest }) => rest);
     } catch {
-      // Ignore malformed draft until valid JSON is provided.
+      this.jsonDrafts.update(drafts => ({ ...drafts, [widgetId]: raw }));
+      this.jsonErrors.update(errors => ({ ...errors, [widgetId]: this.translate.t('builder.widgetJsonInvalid') }));
     }
   }