fix: widen actions_taken to list[Any] and improve bot error replies

DispatchResponse declared actions_taken as list[dict] but agents return
list[str], causing a 422 on every successful upload.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addons/activeblue_ai/models/ab_ai_mail.py

@@ -117,9 +117,24 @@ def _agent_thread(db: str, uid: int, text: str, att_data: list,
                      'I could not process your request right now.'
     except _requests.exceptions.Timeout:
         reply_text = 'The request timed out. Please try again.'
+    except _requests.exceptions.HTTPError as exc:
+        # Try to surface the server-side error detail so the user knows what failed
+        detail = ''
+        try:
+            detail = exc.response.json().get('detail') or ''
+        except Exception:
+            pass
+        _logger.error('Agent HTTP error channel=%s status=%s: %s',
+                      channel_id, exc.response.status_code if exc.response else '?', exc)
+        if detail:
+            reply_text = f'The agent returned an error: {detail}'
+        else:
+            reply_text = (f'The agent service returned an unexpected error '
+                          f'(HTTP {exc.response.status_code if exc.response else "?"}). '
+                          f'Please try again or contact your administrator.')
     except Exception as exc:
         _logger.error('Agent thread error channel=%s: %s', channel_id, exc)
-        reply_text = 'I encountered an error. Please try again or contact your administrator.'
+        reply_text = f'I encountered an error: {exc}'
 
     _post_bot_reply(db, channel_id, bot_partner_id, reply_text)