semgrep/semgrep ? reverse-engineered prompt

Build me a fast code scanning tool that can look through a project and find bugs, security issues, and bad coding patterns by matching rules that look like real source code. I want it to support lots of common languages like Python, JavaScript, TypeScript, Java, Go, Ruby, C, and YAML, and I want it to work locally so code doesn’t get uploaded anywhere by default.

It should be usable from the command line, easy to run in CI, and also simple enough to use while coding so people can catch problems early. The results should be clear and practical, with file names, line numbers, and a short explanation of what was found. If possible, make it easy for users to write their own rules in a simple, code like way without having to learn a complicated query language.

Please make it feel fast and polished, and if you need current docs or examples, look them up online while building it.