Extends the push agent (v1.2.0) with the Netdata-style signals the operator
wants: per-core CPU, per-interface network throughput and per-disk I/O
(rates derived in-agent from monotonic /proc counter deltas, with
counter-reset clamping), hardware temperatures (/sys/class/hwmon),
memory-pressure PSI (/proc/pressure), and cached/buffers memory breakdown.
All stdlib-only.
Server side needs no migration — these land as additional rows in the shared
PluginMetric table via _expand_sample_to_metrics. Per-resource series use a
':' in resource_name (host:net:eth0, host:core0, host:temp:Package) so the
existing fleet widget's ':' filter ignores them; host-level totals/max are
emitted at the bare host resource. New sample keys are optional, so older
agents keep ingesting unchanged.
Unit tests for the new parsers, rate/reset logic, and the expander contract.
Data foundation for the Netdata-style host view (task #867).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
