Two fixes:
1. onSettled orphan cleanup (Codex ID=2963834802): add cleanup in the streaming
dispatcher's onSettled callback for cases where the reply pipeline produces no
final payload — e.g. messaging-tool sends suppressed by agent-runner-payloads.ts,
or empty/heartbeat responses. Without this, onPartialReply could create a preview
post that is never finalized or deleted. The cleanup mirrors the existing logic in
#43041 (P5).
2. Initial-send retry storm (Codex ID=2963834806): call stopPatchInterval() in the
sendMessageMattermost catch block, mirroring the existing fix for patchMattermostPost
failures. Without this, a failed initial post attempt (missing post permission, DM
creation failure, etc.) causes the 200ms interval to retry indefinitely for the rest
of the response, flooding the API and gateway logs.
e2c4d8bd45