🧹fix: Handle Abort Message Edge Cases (#1462)

* chore: bump langchain to v0.0.213 from v0.0.186

* fix: handle abort edge cases:
- abort message server-side if response experienced error mid-generation
- attempt to recover message if aborting resulted in error
- if abortKey is not provided, use conversationId if it exists
- if headers were already sent, send an Event stream message
- issue warning for possible Google censor/filter

refactor(streamResponse): for `sendError`, allow passing overrides so that error can include partial generation, improve typing for `sendMessage`

* chore(MessageContent): remove eslint warning for unused `i`, rephrase unfinished message text

* fix(useSSE): avoid invoking cancelHandler if the abort response was 404

* chore(TMessage): remove unnecessary, unused legacy message property `submitting`

* chore(TMessage): remove unnecessary legacy message property `cancelled`

* chore(abortMiddleware): remove unused `errorText` property to avoid confusion

client/src/components/Nav/ExportConversation/ExportModal.jsx

@@ -172,10 +172,6 @@ export default function ExportModal({ open, onOpenChange, conversation }) {
           fieldName: 'unfinished',
           fieldValues: entries.find((e) => e.fieldName == 'unfinished').fieldValues,
         },
-        {
-          fieldName: 'cancelled',
-          fieldValues: entries.find((e) => e.fieldName == 'cancelled').fieldValues,
-        },
         {
           fieldName: 'messageId',
           fieldValues: entries.find((e) => e.fieldName == 'messageId').fieldValues,
@@ -226,9 +222,6 @@ export default function ExportModal({ open, onOpenChange, conversation }) {
       if (message.unfinished) {
         data += '*(This is an unfinished message)*\n';
       }
-      if (message.cancelled) {
-        data += '*(This is a cancelled message)*\n';
-      }
       data += '\n\n';
     }
 
@@ -275,9 +268,6 @@ export default function ExportModal({ open, onOpenChange, conversation }) {
       if (message.unfinished) {
         data += '(This is an unfinished message)\n';
       }
-      if (message.cancelled) {
-        data += '(This is a cancelled message)\n';
-      }
       data += '\n\n';
     }