e945a357f7
Issue #38: warn_reset_hwm() silently swallowed non-permission I/O errors from /proc/self/clear_refs (e.g. missing /proc, read-only procfs, kernel incompatibility). This left users unaware that VmHWM reset failed and memory peak data could be contaminated across suites. Changes: - runner.rs: all errors now produce a warning with specific failure reason; PermissionDenied retains 'try running as root' hint; AtomicBool warn-once prevents duplicate output across 7 suite runs - main.rs: preflight check now uses warn_reset_hwm() instead of the vague can_reset_vm_hwm(), sharing the same warn-once mechanism - metrics.rs: remove dead can_reset_vm_hwm() (no callers remaining) - tests: add hwm_warned_flag_prevents_reentry and warn_reset_hwm_does_not_panic