fix(assistant): unlock configuration after failed request

src/app/shared/flow-assistant/flow-assistant.css

@@ -251,7 +251,7 @@
 }
 
 .assistant-advanced-toggle,
-.assistant-new-session {
+.assistant-advanced-toggle {
   justify-self: start;
   border: 0;
   padding: 0;

src/app/shared/flow-assistant/flow-assistant.html

@@ -45,11 +45,6 @@
           <p class="assistant-label">Configurazione assistente</p>
           <p class="assistant-copy">Le credenziali dei provider sono gestite dal backend.</p>
         </div>
-        @if (configurationLocked()) {
-        <button type="button" mat-stroked-button class="assistant-new-session" [disabled]="assistantBusy()" (click)="createNewSession()">
-          Nuova sessione
-        </button>
-        }
       </div>
 
       <mat-checkbox
@@ -60,7 +55,7 @@
       </mat-checkbox>
 
       @if (configurationLocked()) {
-      <p class="assistant-meta">La configurazione LLM è fissata per questa sessione. Crea una nuova sessione per modificarla.</p>
+      <p class="assistant-meta">La configurazione LLM è fissata per questa sessione.</p>
       }
 
       @if (!useDefaultConfiguration()) {

src/app/shared/flow-assistant/flow-assistant.ts

@@ -277,18 +277,6 @@ export class FlowAssistant implements OnInit, OnDestroy {
     this.persistSnapshot();
   }
 
-  createNewSession() {
-    if (this.assistantBusy() || !this.configurationValid()) return;
-    this.stopPolling();
-    this.currentCall.set(null);
-    this.sessionState.set(null);
-    this.localMessages.set([]);
-    this.assistantErrorMessage.set(null);
-    this.lastFailedPrompt.set(null);
-    this.lastSubmittedPrompt.set('');
-    void this.openSession();
-  }
-
   useStarter(prompt: string) {
     this.prompt.set(prompt);
     this.persistSnapshot();
@@ -388,6 +376,7 @@ export class FlowAssistant implements OnInit, OnDestroy {
       error: (err) => {
         console.error('Assistant flow action failed', err);
         this.requestPending.set(false);
+        this.discardFailedSession();
         this.handleAssistantErrorWithRetry(normalizedContent, this.backendErrorMessage(err));
       }
     });
@@ -505,6 +494,12 @@ export class FlowAssistant implements OnInit, OnDestroy {
     this.syncDraftToEditor(result.flow);
   }
 
+  private discardFailedSession() {
+    this.stopPolling();
+    this.currentCall.set(null);
+    this.sessionState.set(null);
+  }
+
   private backendErrorMessage(error: unknown): string {
     const value = error as { error?: unknown; message?: unknown };
     const payload = value?.error;