level-2: add --severity flag + PowerShell own-check.ps1 #1 --severity {error,warning} (default error): threaded through the core renderer (Finding.render/_github/_msbuild + render_finding), the ownir CLI (--severity, validated; only valid for ownir), own-check.sh, and the composite Action's new 'severity' input. A presentation choice — the finding is still the core's verdict — so a build can show leaks as advisory warnings instead of failing. Resolves P-013 open question #1. #2 scripts/own-check.ps1: a PowerShell twin of own-check.sh so Windows/VS users without bash get the same one-command pipeline (same flags/output). #11