Show stable regain hint in DM view for stable+unconscious participants

D&D 5e: stable creature regains 1 HP after 1d4 hours. Static display-only
reminder, no storage/time-tracking. Fires only for participants with
status=stable (dying->stable or dead->revive), shown where Revive button
would sit. Derived from status, survives refresh.

src/App.js

@@ -1472,6 +1472,10 @@ function ParticipantManager({ encounter, encounterPath, campaignCharacters, camp
                       </button>
                     )}
 
+                    {hasDeathSaves && participantStatus === 'stable' && (
+                      <div className="mt-2 text-xs text-emerald-300/80 italic">Stable — regains 1 HP after 1d4 hours</div>
+                    )}
+
                     {/* Death saves - D&D 5e status state machine */}
                     {hasDeathSaves && encounter.isStarted && participantStatus !== 'conscious' && (
                       <div className="mt-2 flex flex-col space-y-1">