VS Code 扩展

## Role
Act as a senior software engineer.

## Objective
Add rate limiting to the public API.

## Requirements
- Make sure existing clients keep working.
- Follow the conventions, naming, and structure already used in the codebase.
- Handle invalid input and failure paths explicitly.

## Constraints
- Do not change unrelated code, and do not add dependencies unless the task requires them.
- Keep existing public interfaces and API contracts unchanged.

## Edge cases
- Invalid, missing, and oversized input.
- Unauthenticated, unauthorized, and rate-limited requests.

## Testing
- Success responses: status code and response shape.
- Validation and error responses.
- Add tests for the new behavior, including failure paths.
- Run the existing test suite and report the result.

## Acceptance criteria
- The new behavior works as described in the objective.
- All tests pass and no unrelated files are changed.

## Expected output
- Return every change as a unified diff or as complete new and updated files.
- List the design decisions and assumptions you made.