fix(scan): distinguish active issues from known warnings

[max23468]

Cosa cambia

• usa una sola policy per distinguere problemi attivi e avvisi ignorati
• consente le rimozioni quando restano soltanto avvisi noti
• richiede l’email per problemi non ignorati, inclusa una sitemap malformata

Corregge i due thread Codex emersi dopo il merge della #84.

Verifiche

• npm test (51 test)
• npm run build
• git diff --check
• email verificata con sender mockato; nessun invio reale

[chatgpt-codex-connector]

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