docs(core): add JSDoc documentation to error classes

Author: Dark-Brain07

packages/frames.js/src/core/errors.ts

@@ -1,22 +1,36 @@
+/**
+ * Error thrown when the request body cannot be parsed as JSON.
+ * This typically occurs when the frame action payload is malformed.
+ */
 export class RequestBodyNotJSONError extends Error {
   constructor() {
     super("Invalid frame action payload, request body is not JSON");
   }
 }
 
+/**
+ * Error thrown when the frame action payload is invalid.
+ * This occurs when the payload doesn't contain the expected structure.
+ */
 export class InvalidFrameActionPayloadError extends Error {
   constructor(message = "Invalid frame action payload") {
     super(message);
   }
 }
 
+/**
+ * Error class for frame message validation errors.
+ * Used to return user-facing error messages with appropriate HTTP status codes.
+ */
 export class FrameMessageError extends Error {
   status: number;
 
   /**
-   *
+   * Creates a new FrameMessageError.
    * @param message - Message to show the user (up to 90 characters)
-   * @param status - 4XX status code
+   * @param status - HTTP status code (must be 4XX)
+   * @throws Error if message exceeds 90 characters
+   * @throws Error if status code is not in 4XX range
    */
   constructor(message: string, status: number) {
     if (message.length > 90) throw new Error("Message too long");
@@ -26,3 +40,4 @@ export class FrameMessageError extends Error {
     this.status = status;
   }
 }
+