Hour-long remote tasks were never delivered: a subscribe watch held one SSE stream for up to a day, the remote
sent nothing while its agent worked without text, and once the quiet connection died on the way (no FIN/RST) the
watch waited on it with no error and no log line.
- A subscription lasts at most 5 minutes (SubscriptionSlice), then GetTask and a new subscription: a pause, not a
failure. A slice ended mid-read counts as ours even when it surfaces as an I/O error.
- The shared handler connects with TCP keepalive (60 s, every 15 s, 4 probes) and HTTP/2 pings.
- Log lines when a watch starts or is restored, when a slice ends on a running task, when a result is delivered or
kept; the Telegram host's console log carries a UTC timestamp.
- action=status on a settled task ends its watch, so the result isn't delivered a second time.
- A "context busy" refusal of send says nothing was sent, names the watched task in that context and that its
result will arrive by itself; refusals never touch a watch.
File parts were only taken from artifacts as inline bytes up to 10 MB; parts in the
status message or the history were dropped silently, URL parts were never downloaded,
and a plain message reply lost its files. Files now go to inbox/a2a/<taskId>/ from
artifacts, status message and recent agent messages (deduplicated), URLs are streamed
to disk (agent key only on the agent's origin, else https without it), the cap is the
new MaxReceivedFileBytes (200 MB), and results list path, bytes and media type or why
a file was not saved. Re-saving a task overwrites, so action=status refetches files.
