🤖 fix: cancel active stream on message edit to prevent history corruption

When editing a compacting message to change parameters (e.g., token count)
while the first compaction is still streaming, the old stream would continue
and corrupt the chat history by replacing everything with [truncated].

Root cause: handleCompletion would find the NEW compaction request in history
and proceed to perform compaction with the OLD stream's partial summary.

Fix: Cancel any active stream before processing edits. This ensures only one
stream runs at a time and aligns with user intent (edit = discard old).

Impact: 9 lines added to agentSession.ts sendMessage method

Author: ethanndickson

src/node/services/agentSession.ts

@@ -270,6 +270,13 @@ export class AgentSession {
       );
     }
 
+    if (options?.editMessageId && this.aiService.isStreaming(this.workspaceId)) {
+      const stopResult = await this.interruptStream(/* abandonPartial */ true);
+      if (!stopResult.success) {
+        return Err(createUnknownSendMessageError(stopResult.error));
+      }
+    }
+
     if (options?.editMessageId) {
       const truncateResult = await this.historyService.truncateAfterMessage(
         this.workspaceId,