v0.3.3

Fix the Telegram poller watchdog/heartbeat timing race: the poller child now heartbeats immediately before each poll, so a slow poll no longer false-trips the 30s watchdog and gets killed right after a fresh start. Includes a regression test (test/test-poller-heartbeat.py). Also switch courier.log to append mode so a hung instance's evidence survives across leader restarts.

No public API change; patch release.