fix(host/windows): clippy while_let_loop in the async poll drain

The rebase onto main picked up the pre-fix loop{match} variant of the
async retrieve drain — the exact shape the Windows clippy gate rejects
(run 6722 failed on it; the while-let form passed run 6724 on the CI
branch). Restore the gated form.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/punktfunk-host/src/encode/windows/nvenc.rs

@@ -1174,17 +1174,13 @@ impl Encoder for NvencD3d11Encoder {
         // the oldest ready AU. `None` = nothing completed yet — the session loop keeps the frame
         // in flight and re-polls next tick, capture never blocks on the WDDM scheduling wait.
         if self.async_rt.is_some() {
-            loop {
-                let done = match self
+            while let Ok(done) = self
                 .async_rt
                 .as_mut()
                 .expect("checked just above")
                 .done_rx
                 .try_recv()
             {
-                    Ok(d) => d,
-                    Err(_) => break,
-                };
                 self.absorb_done(done)?;
             }
             return Ok(self