LazyProc.Call must-finds and panics on a missing export; the trimmed
Tianyi cloud-PC image has no FreeMibIfTable2 in iphlpapi.dll, which
killed the agent on its first collection after a successful register.
Optional procs (GetSystemTimes/GlobalMemoryStatusEx/GetIfTable2Ex+
FreeMibIfTable2 as one gated pair) now resolve through sourceGate
(Find once, missing = source disabled with one warning); the iface
pair is gated together so a missing free proc never leaks the
system table. collectMetrics additionally runs every source through
guardedCall so any residual panic zeroes that source alone.
Pure gate/guard logic lives in probe_guard.go (no build tag) with
Linux-runnable regression tests.
Muse
92dfdc542c