samedec: flush on EOF in main app

Previously, `samedec::app::run()` would unceremoniously exit on
EOF. Since an EOF results in samples being "stranded" in filter
buffers and other parts of the system, it is necessary to push
zeros through the system to make it output any remaining
Messages.

This "flush" operation was performed by isolated code that ran
after the app terminated. This would print the Message(s), but it
would not take any other actions like spawning child processes.

We should spawn the child even if there's no audio data that
follows. The state machine will simply `wait()` for it to
terminate and then exit.

This change permits us to run child processes on short snippets of
SAME data—i.e., our `sample/*.bin` data files.

This is CLI-expanding behavior.

crates/samedec/src/app.rs

@@ -114,7 +114,8 @@ impl State<Waiting> {
             return Some(msg.into());
         }
 
-        None
+        // end of file; flush any remaining messages out of the decoder
+        Some(receiver.flush()?.into())
     }
 }
 

crates/samedec/src/main.rs

@@ -48,16 +48,6 @@ fn samedec() -> Result<(), CliError> {
         std::iter::from_fn(|| Some(inbuf.read_i16::<NativeEndian>().ok()?)),
     );
 
-    // flush all data samples out of the decoder
-    match rx.flush() {
-        Some(lastmsg) => {
-            if !args.quiet {
-                println!("{}", lastmsg)
-            }
-        }
-        None => {}
-    }
-
     Ok(())
 }