Fix bug for create new file on toolchain project

[q-inho]

Resolve #57

Fix

• The create_new_file function now creates a mirrored documentation file whenever a new .hat source file is created inside a project. The docs file is placed under src/hat_docs/ with the same relative path as the source file and a .md extension.
• Before creating a file, te tool now checkts that the target path resides within the current project's directory. If the resolved file path is outside the project, the operation is aborted with an error.
• CLI ensures the users run hat new -f from within an existing project. If not, it reports a n error adn stops.
• If the providedf ile path does not start wit hsrc/, it is automatically prefixed with src/ so that new files are placed in the correc tproject subdirectory.
• The .hat extension is appended if it's missing from the given filename, ensuring connsistency.
• If either the target source file or its documentation file already, it fail with an error isntead of overwriting them.