feat: luck bonus, inventory slots bonus, multi-enhancements, magic skill modifier

- Add luck.bonus field to character DataModel; included in prepareDerivedData
   (luck.max = fate.rank + bonus); shown as editable +bonus field next to
   luck max in edit mode (same UX as grit bonus)

 - Add inventory.slotsBonus field to character DataModel; Equipment tab now
   shows an editable "Bonus Slots" input that adds to the calculated max slots
   (10 + Might×2 + bonus)

 - Replace single Enhancement <select> in spell cast dialog with a checkbox
   list; multiple enhancements can now be selected simultaneously — stress
   costs, pool penalties, and boolean flags (redDice, noStress) are aggregated
   across all active enhancements

 - Include skills.magic.modifier in basePool for both spell and miracle dialogs
   and in baseDice in rollSpellCast / rollMiracleCast; modifier is shown in
   the dialog pool-info line and in the chat card when non-zero

 - Fix: pool-reduction indicator in rollSpellCast now compares against
   intRank + magicRank + magicMod (was missing magicMod)

module/applications/sheets/character-sheet.mjs

@@ -39,6 +39,7 @@ export default class OathHammerCharacterSheet extends OathHammerActorSheet {
       adjustCurrency:  OathHammerCharacterSheet.#onAdjustCurrency,
       adjustLuck:      OathHammerCharacterSheet.#onAdjustLuck,
       adjustGrit:      OathHammerCharacterSheet.#onAdjustGrit,
+      adjustStress:    OathHammerCharacterSheet.#onAdjustStress,
       clearStress:     OathHammerCharacterSheet.#onClearStress,
     },
   }
@@ -190,8 +191,8 @@ export default class OathHammerCharacterSheet extends OathHammerActorSheet {
           }
         })
         context.ammunition = doc.itemTypes.ammunition
-        // Slot tracking: max = 10 + (Might rank × 2); used = sum of all items' slots × quantity
-        context.slotsMax = 10 + (doc.system.attributes.might.rank * 2)
+        // Slot tracking: max = 10 + (Might rank × 2) + bonus; used = sum of all items' slots × quantity
+        context.slotsMax = 10 + (doc.system.attributes.might.rank * 2) + (doc.system.inventory?.slotsBonus ?? 0)
         context.slotsUsed = doc.items.reduce((sum, item) => {
           const qty = item.system.quantity ?? 1
           return sum + (item.system.slots ?? 0) * Math.max(qty, 1)
@@ -225,7 +226,7 @@ export default class OathHammerCharacterSheet extends OathHammerActorSheet {
           id: m.id, uuid: m.uuid, img: m.img, name: m.name, system: m.system,
           _descTooltip: _stripHtml(m.system.description)
         }))
-        context.slotsMax = 10 + (doc.system.attributes.might.rank * 2)
+        context.slotsMax = 10 + (doc.system.attributes.might.rank * 2) + (doc.system.inventory?.slotsBonus ?? 0)
         context.slotsUsed = doc.items.reduce((sum, item) => {
           const qty = item.system.quantity ?? 1
           return sum + (item.system.slots ?? 0) * Math.max(qty, 1)