Reads a file from the local filesystem.

- `file_path` must be an absolute path.
- Reads up to 2000 lines by default.
- When you already know which part of the file you need, only read that part. This can be important for larger files.
- Results are returned using cat -n format, with line numbers starting at 1
- Reads images (PNG, JPG, …) and presents them visually. Reads PDFs via the `pages` parameter (e.g. "1-5", max 20 pages/request; required for PDFs over 10 pages). Reads Jupyter notebooks (.ipynb) as cells with outputs.
- Reading a directory, a missing file, or an empty file returns an error or system reminder rather than content.
- Do NOT re-read a file you just edited to verify — Edit/Write would have errored if the change failed, and the harness tracks file state for you.