Add __main__.py to allow running amifuse as a Python module

Without __main__.py, "python3 -m amifuse" fails with:

  No module named amifuse.__main__; 'amifuse' is a package and
  cannot be directly executed

Add the module entry point and set prog="amifuse" in ArgumentParser
so that usage messages show "amifuse" rather than "__main__.py".

Document "python3 -m amifuse" as an alternative to pip-installing
the package, useful for development and debugging from a local
checkout.

Author: reinauer

README.md

@@ -67,6 +67,14 @@ sudo apt install fuse libfuse-dev
 sudo dnf install fuse fuse-devel
 ```
 
+### Running from source (without installing)
+
+To run amifuse directly from a local checkout (useful for development/debugging):
+
+```bash
+python3 -m amifuse mount disk.hdf
+```
+
 ## Quick Start
 
 To download a test PFS3 disk image and the pfs3aio handler:

amifuse/__main__.py

@@ -0,0 +1,3 @@
+from amifuse.fuse_fs import main
+
+main()

amifuse/fuse_fs.py

@@ -2355,6 +2355,7 @@ def cmd_format(args):
 
 def main(argv=None):
     parser = argparse.ArgumentParser(
+        prog="amifuse",
         description=f"{__banner__}\n\n"
         "Mount Amiga filesystem images via FUSE.",
         formatter_class=argparse.RawDescriptionHelpFormatter,