compile writes a .masb artifact that no other CLI command can read

### Packages versions

miden-vm: 0.30.0 (`next`, 5d9716449)

### Bug description

`miden-vm compile` writes its output with a `.masb` extension, and nothing else in the CLI reads that. Both `run` and `prove` accept only `.masm` and `.masp`, so the compiled artifact is turned away on the extension alone.

Renaming it doesn't help either. `compile` serializes a `Program`, whose magic is `MAST\0`, while the `.masp` path deserializes a `Package`, whose magic is `MASP\0`, so the rename just moves the failure from the extension check to the magic-byte check.

The result is that `compile` succeeds, prints a program hash, and leaves behind a file no other subcommand can consume.

https://github.com/0xMiden/miden-vm/blob/5d97164493d2c441c306b9b2dbb1ad2fa67a2a3a/miden-vm/src/cli/compile.rs#L45-L49

`masb` appears nowhere else in the tree apart from those two lines and one 2024 changelog entry, so the extension looks left over from before packages replaced raw serialized programs — `run` and `prove` were moved to `.masp`, `compile` wasn't.

### How can this be reproduced?

```sh
printf 'begin\n push.1 push.2 add\nend\n' > prog.masm

miden-vm compile -a prog.masm # writes prog.masb
miden-vm run prog.masb # rejected on the extension
cp prog.masb prog.masp
miden-vm run prog.masp # rejected on the magic bytes
```

`prove` behaves the same way as `run` for both steps.

### Relevant log output

```shell
$ miden-vm compile -a prog.masm
program hash is 2cc8f31f945a01207647f2790c386f5d3a98ea9979a7645e8ce372b1b9b213db

$ ls prog.*
prog.inputs prog.masb prog.masm

$ miden-vm run prog.masb
Error: x The provided file must have a .masm or .masp extension

$ miden-vm run prog.masp
Error: x Failed to deserialize package
`-> invalid value: invalid magic bytes. Expected '[77, 65, 83, 80, 0]', got
'[77, 65, 83, 84, 0]'
```

I'd be happy to take this on and submit a PR to fix the serialization/extension mismatch. Could you please assign this issue to me?