The server inferred each plugin's collection interval from the gap between
the last two received PLG samples, then expired data at interval * 3. After
an outage this guess was wrong: the request_update re-send of collect-once
InfoPlugins produced two close samples, yielding a tiny inferred interval
that purged permanent info data minutes after recovery.
Clients now declare each plugin's interval in the PLG message (_interval).
The server uses it directly (from the first post-recovery sample), expiring
at interval * 3 so live data survives at least two full intervals; interval
0 marks collect-once InfoPlugins that never go stale. Legacy clients omit
the field and fall back to the previous inferred-gap behavior.
Adds _interval to all three clients: hbc, hbc_mini.py, hbc_mini.c.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>