fix(encode/windows): a stale PUNKTFUNK_ENCODER pin no longer wedges a conflicting GPU selection

On a hybrid box, picking a GPU in the web console whose vendor contradicts a
host.env PUNKTFUNK_ENCODER pin produced an unrecoverable session: the pin won
backend selection while the adapter followed the console, the wrong-vendor
encoder failed deterministically at submit, the reset ladder burned its 5
in-place rebuilds on it, and the client reconnected into the identical wall
forever (~10 s per cycle, no visible reason).

Three legs:
- windows_resolved_backend() now reconciles: a hardware pin whose vendor
  contradicts the selected GPU is overridden by the adapter-derived backend
  (capture + encode share one adapter, so honoring the pin can only fail);
  open_video warns loudly when a pin loses. The reconciliation is a pure,
  unit-tested table (resolve_windows_backend).
- the QSV wrong-adapter bind is typed TerminalEncoderError, and the stream
  loop's reset ladder ends the session immediately on it instead of feeding a
  deterministic config error 5 futile rebuilds.
- the un-pinned path was already correct (verified on-glass: NVIDIA preference
  + no pin = stable AV1 10-bit HDR on NVENC), so the override simply takes the
  conflict case onto that path.

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

crates/punktfunk-host/src/native/stream.rs

@@ -2329,6 +2329,19 @@ pub(super) fn virtual_stream(ctx: SessionContext, prepared: Option<PreparedDispl
         // assign next. The RFI backends pin their frame numbering to it.
         let wire_index = au_seq.wrapping_add(inflight.len() as u32);
         if let Err(e) = enc.submit_indexed(&frame, wire_index) {
+            // A typed-terminal error is a deterministic configuration failure — the identical
+            // wall on every attempt, so rebuilds can't help. End the session at once with the
+            // carried cause (observed: a stale PUNKTFUNK_ENCODER pin vs. the selected adapter
+            // burned all 5 rebuilds per connect while the client reconnected forever).
+            if e.downcast_ref::<crate::encode::TerminalEncoderError>()
+                .is_some()
+            {
+                tracing::error!(
+                    error = %format!("{e:#}"),
+                    "encoder failed with a deterministic configuration error — ending the video \
+                     session without rebuild attempts (see the error for the remedy)");
+                return Err(e).context("encoder submit");
+            }
             // The input half of an encode stall: once the driver stops draining AUs, libavcodec's
             // one-frame buffer fills and avcodec_send_frame starts failing (EAGAIN) — the same
             // wedge the watchdog below catches, seen from submit. Rebuild the encoder in place