fix(config-editor): coerce deleted keys to null in local computePatches

Aligns with canonical config-utils.ts:66 — keys absent from modObj or
explicitly set to undefined now emit null in the patch value instead of
undefined, preventing stale/invalid patch payloads on key deletion.

Author: BillChirico

web/src/components/dashboard/config-editor.tsx

@@ -1809,7 +1809,8 @@ function computePatches(
       ) {
         walk(origVal as Record<string, unknown>, modVal as Record<string, unknown>, fullPath);
       } else {
-        patches.push({ path: fullPath, value: modVal });
+        const patchValue = !Object.hasOwn(modObj, key) || modVal === undefined ? null : modVal;
+        patches.push({ path: fullPath, value: patchValue });
       }
     }
   }