auto-recover corrupted conversations on API error

when append_conversation fails (422, 404, etc.), the stale mapping
is deleted and a fresh conversation is created automatically.
prevents Sol from being permanently stuck after a hung research
session or Mistral API error.

src/conversations.rs

@@ -81,10 +81,10 @@ impl ConversationRegistry {
     ) -> Result<ConversationResponse, String> {
         let mut mapping = self.mapping.lock().await;
 
+        // Try to append to existing conversation; if it fails, drop and recreate
         if let Some(state) = mapping.get_mut(room_id) {
-            // Existing conversation — append
             let req = AppendConversationRequest {
-                inputs: message,
+                inputs: message.clone(),
                 completion_args: None,
                 handoff_execution: None,
                 store: Some(true),
@@ -92,24 +92,38 @@ impl ConversationRegistry {
                 stream: false,
             };
 
-            let response = mistral
+            match mistral
                 .append_conversation_async(&state.conversation_id, &req)
                 .await
-                .map_err(|e| format!("append_conversation failed: {}", e.message))?;
+            {
+                Ok(response) => {
+                    state.estimated_tokens += response.usage.total_tokens;
+                    self.store.update_tokens(room_id, state.estimated_tokens);
 
-            // Update token estimate
+                    debug!(
-            state.estimated_tokens += response.usage.total_tokens;
+                        room = room_id,
-            self.store.update_tokens(room_id, state.estimated_tokens);
+                        conversation_id = state.conversation_id.as_str(),
+                        tokens = state.estimated_tokens,
+                        "Appended to conversation"
+                    );
 
-            debug!(
+                    return Ok(response);
-                room = room_id,
+                }
-                conversation_id = state.conversation_id.as_str(),
+                Err(e) => {
-                tokens = state.estimated_tokens,
+                    warn!(
-                "Appended to conversation"
+                        room = room_id,
-            );
+                        conversation_id = state.conversation_id.as_str(),
+                        error = e.message.as_str(),
+                        "Conversation corrupted — dropping and creating fresh"
+                    );
+                    self.store.delete_conversation(room_id);
+                    mapping.remove(room_id);
+                    // Fall through to create a new conversation below
+                }
+            }
+        }
 
-            Ok(response)
+        {
-        } else {
             // New conversation — create (with optional context hint for continuity)
             let agent_id = self.agent_id.lock().await.clone();