Split FastAPI debug config into file-scoped and project-scoped options

Hey folks 👋 I work at @fastapilabs and maintain https://github.com/fastapi/fastapi-vscode. I've been looking at the broader FastAPI experience in VS Code and wanted to open an issue to discuss an improvement we've been discussing related to debugging.

The current FastAPI debug configurations (the snippet from microsoft/vscode-python#14606 and the dynamic provider added in #19505) launch the app via uvicorn ...:app --reload and rely on hand-rolled main.py detection. This predates the fastapi CLI (fastapi run / fastapi dev), which provides built-in app discovery via pyproject.toml or default file locations.

For an improved experience, I'd like to propose splitting the current debugging experience into two options:

• Debug FastAPI with current file - runs fastapi run ${file} against the currently active file. This is optimal for single-file apps or quickly debugging a specific entry point.

• Debug FastAPI - runs plain fastapi run and lets the CLI discover the app via pyproject.toml or default file locations. Doing this would also remove the extension's own detection logic in favor of the FastAPI CLI's resolution, and give users a clearer choice between file-scoped and project-scoped debugging.

Wanted to gauge whether there'd be appetite for this change. I already have a branch with most of this working locally and would be happy to put up a PR if it makes sense.

Thanks!

Beginne damit, die aktuellen FastAPI-Debug-Konfigurationen und den im Issue beschriebenen dynamischen Provider sowie die referenzierten Änderungen an vscode-python zu prüfen. Vergleiche deren Erkennung von uvicorn und main.py mit der Datei- und Projekterkennung der fastapi CLI über pyproject.toml. Erledigt ist die Aufgabe, wenn die Debugging-Erfahrung mithilfe der CLI klar getrennte Optionen für die aktuelle Datei und den Projektbereich bietet.