feat: T2A defensive spells (#2378)

## Summary

Implements T2A-accurate mechanics for the three defensive spells based on UO98 demo scripts. Pre-UOR (`!Core.UOR`) triggers the new behavior; UOR and AOS paths are unchanged.

- **Reactive Armor**: percentage-based melee damage reflection (10-35% based on target Magery), targeted, timed (25-75s). Guards exempt, ranged attacks beyond 1 tile unaffected. Reflected damage is sourceless.
- **Protection**: temporary AC bonus (casterMagery/10, 1-10 AR) via VirtualArmorMod, targeted, timed (12-120s). Shared table with Arch Protection — only one protection buff per mobile.
- **Magic Reflect**: single-use spell reflection using MagicDamageAbsorb as a flag. No timer, no DefensiveSpell lock. Consumed on first reflected spell.
- **Arch Protection**: T2A path applies Protection via shared table with area sound (0x1F7 vs 0x1ED).
- No DefensiveSpell mutual exclusion for T2A — all three spells operate independently.

## Test plan

- [x] Set expansion to T2A
- [x] Cast Reactive Armor on self → verify particles (0x376A) and sound (0x1F2)
- [x] Get hit in melee → verify attacker takes reflected damage with spark effect and sound
- [x] Get hit by ranged weapon from > 1 tile → verify no reflection
- [x] Wait for RA to expire → verify effect ends silently
- [x] Cast RA on target that already has it → verify "This spell is already in effect"
- [x] Cast Protection on another player → verify particles (0x375A) and sound (0x1ED)
- [x] Check target's AR → verify it increased by casterMagery/10
- [x] Wait for Protection to expire → verify AR returns to normal
- [x] Cast Protection on self, then cast Protection on another player → verify both succeed
- [x] Cast Arch Protection on ground near allies → verify each gets AR bonus with sound 0x1F7
- [x] Cast Arch Protection near a target already protected → verify that target is skipped
- [x] Cast Magic Reflect on self → verify particles (0x375A) and sound (0x1E9)
- [x] Have an enemy cast a harmful spell at you → verify spell reflects back, effect consumed
- [x] Cast Magic Reflect again → verify it can be recast after consumption
- [x] Cast Magic Reflect when already active → verify "This spell is already in effect"
- [x] Verify all three spells can be active simultaneously on the same mobile
- [x] Switch expansion to UOR → verify existing UOR behavior unchanged
- [x] Switch expansion to AOS → verify existing AOS behavior unchanged

Projects/UOContent/Spells/Base/SpellHelper.cs

@@ -893,16 +893,25 @@ namespace Server.Spells
 
             if (target.MagicDamageAbsorb > 0)
             {
-                ++circle;
-
-                target.MagicDamageAbsorb -= circle;
-
-                // This order isn't very intuitive, but you have to nullify reflect before target gets switched
-                reflect = target.MagicDamageAbsorb >= 0;
-                if (target.MagicDamageAbsorb <= 0)
+                if (!Core.UOR)
                 {
+                    // T2A: single-use reflection, consumed immediately
                     target.MagicDamageAbsorb = 0;
-                    DefensiveSpell.Nullify(target);
+                    reflect = true;
+                }
+                else
+                {
+                    ++circle;
+
+                    target.MagicDamageAbsorb -= circle;
+
+                    // This order isn't very intuitive, but you have to nullify reflect before target gets switched
+                    reflect = target.MagicDamageAbsorb >= 0;
+                    if (target.MagicDamageAbsorb <= 0)
+                    {
+                        target.MagicDamageAbsorb = 0;
+                        DefensiveSpell.Nullify(target);
+                    }
                 }
             }