fix(inventory): ensure stored locations always initialized properly

Fixes Bug #3: Locations disappearing when switching tabs or on reload.

Root cause: inventory.stored could become corrupted (null, array, or
undefined) due to incomplete validation during load/save operations.

Solution - Defense in Depth:

1. **Persistence Layer** (src/core/persistence.js):
   - New validateInventoryStructure() function
   - Validates on loadSettings() and loadChatData()
   - Checks all v2 fields (onPerson, stored, assets, version)
   - Ensures stored is always a plain object
   - Validates stored keys/values using validateStoredInventory()
   - Auto-repairs corrupted data with console warnings
   - Persists repairs immediately

2. **Form State Management** (src/systems/interaction/inventoryActions.js):
   - Enhanced restoreFormStates() to detect deleted locations
   - Cleans up orphaned form states automatically
   - Prevents errors from forms referencing non-existent locations

Validation checks:
- ✓ inventory.stored is object (not null/array/undefined)
- ✓ All stored keys are safe (no __proto__, constructor, etc.)
- ✓ All stored values are strings
- ✓ onPerson and assets are strings
- ✓ version field exists

Auto-repair scenarios:
- Corrupted stored → reset to {}
- Invalid onPerson/assets → reset to "None"
- Missing version → set to 2
- Dangerous keys → removed with warning

Result:
- Locations persist across tab switches ✓
- Empty locations persist ✓
- Data corruption auto-repaired on load ✓
- Orphaned form states cleaned up ✓
- No crashes from invalid data ✓

Fixes: Location disappears when switching tabs or reloading

src/systems/interaction/inventoryActions.js

@@ -539,6 +539,7 @@ export function getInventoryRenderOptions() {
 /**
  * Restores the state of inline forms after re-rendering.
  * This ensures forms that were open before re-render are shown again.
+ * Also cleans up orphaned form states for deleted locations (Bug #3 fix).
  */
 export function restoreFormStates() {
     // Restore add location form
@@ -570,15 +571,31 @@ export function restoreFormStates() {
     }
 
     // Restore add item stored forms (for each location)
+    // Clean up orphaned states for deleted locations (Bug #3 fix)
     if (openForms.addItemStored && typeof openForms.addItemStored === 'object') {
+        const inventory = extensionSettings.userStats.inventory;
+        const locationsToDelete = [];
+
         for (const location in openForms.addItemStored) {
             if (openForms.addItemStored[location]) {
-                const locationId = location.replace(/\s+/g, '-');
-                const form = $(`#rpg-add-item-form-stored-${locationId}`);
-                if (form.length > 0) {
-                    form.show();
+                // Check if location still exists in inventory
+                if (inventory?.stored && inventory.stored.hasOwnProperty(location)) {
+                    // Location exists, restore form
+                    const locationId = location.replace(/\s+/g, '-');
+                    const form = $(`#rpg-add-item-form-stored-${locationId}`);
+                    if (form.length > 0) {
+                        form.show();
+                    }
+                } else {
+                    // Location was deleted, mark for cleanup
+                    locationsToDelete.push(location);
                 }
             }
         }
+
+        // Clean up orphaned form states
+        for (const location of locationsToDelete) {
+            delete openForms.addItemStored[location];
+        }
     }
 }