Retest issues

Every open issue gets automatically re-checked on each Explore run, not just tracked. Most of the lifecycle below happens on its own; only Confirmed and Ignored are things a person decides, and once decided, Quail respects them.

• New and Still present move on their own: found or re-found by Explore. A retest that no longer reproduces either one promotes it straight to Fixed
• Confirmed (manual only): your team has signed off that it's real. A retest that still reproduces it leaves it Confirmed — it never quietly slides back down to Still present
• Ignored (manual only): permanently excluded from retesting. Even if Explore stumbles onto the exact same bug again later, it won't reopen
• Fixed is automatic: set the moment a retest can no longer reproduce the issue, from any open state, Confirmed included — a real recheck, not just time passing
• Regressions aren't buried: a Fixed issue that reproduces again on a later Explore run reopens as Still present
• A severity threshold controls how far down the list each run actively re-verifies, set from Explore → Retest issues