Handle nullable arrays in tool inputSchemas

* In DynamicJsonForm.tsx
  - In debouncedUpdateParent, formatJson, and validateJson,
    - when trimming the JSON value, use ?.trim() in case the field is null

* In jsonUtils.ts
  - in tryParseJson
    - use ?.trim() in case the field is null

* In schemaUtils.ts
  - in normalizeUnionType
    - add condition to handle the case where there is an anyOf with array or null as options

* In ToolsTab.tsx
  - for nullable fields, in null checkbox, in onCheckedChange handler
    - when not checked, if prop type is array, set to undefined (empty input field that can be edited rather than the word "null" as the default could provide

Fixes #846

client/src/utils/schemaUtils.ts

@@ -191,6 +191,16 @@ export function normalizeUnionType(schema: JsonSchemaType): JsonSchemaType {
     return { ...schema, type: "integer", anyOf: undefined, nullable: true };
   }
 
+  // Handle anyOf with exactly array and null (FastMCP pattern)
+  if (
+    schema.anyOf &&
+    schema.anyOf.length === 2 &&
+    schema.anyOf.some((t) => (t as JsonSchemaType).type === "array") &&
+    schema.anyOf.some((t) => (t as JsonSchemaType).type === "null")
+  ) {
+    return { ...schema, type: "array", anyOf: undefined, nullable: true };
+  }
+
   // Handle array type with exactly string and null
   if (
     Array.isArray(schema.type) &&