🤖 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

@@ -271,6 +271,15 @@ export class AgentSession {
     }
 
     if (options?.editMessageId) {
+      // Interrupt an existing stream or compaction, if active
+      if (this.aiService.isStreaming(this.workspaceId)) {
+        // MUST use abandonPartial=true to prevent handleAbort from performing partial compaction
+        // with mismatched history (since we're about to truncate it)
+        const stopResult = await this.interruptStream(/* abandonPartial */ true);
+        if (!stopResult.success) {
+          return Err(createUnknownSendMessageError(stopResult.error));
+        }
+      }
       const truncateResult = await this.historyService.truncateAfterMessage(
         this.workspaceId,
         options.editMessageId