Previously, long-running streamed responses could be incorrectly treated
as idle by the gateway/cron inactivity timeout even while tokens were
actively arriving. The _touch_activity() call (which feeds
get_activity_summary() polled by the external timeout) was either called
only on the first chunk (chat completions) or not at all (Anthropic,
Codex, Codex fallback).
Add _touch_activity() on every chunk/event in all four streaming paths
so the inactivity monitor knows data is still flowing.
Fixes#8760
2773b18b56