footage: node-graph decode uses a ready proxy, tolerate unset stream index

Re-applies the proxy selection (with the -1 tolerance) after the
revert: the node-graph viewer decode must stand in a ready proxy for
the 4K original, and a proxy generated before the stream-index
recording (index -1) still matches the first video stream rather than
silently falling back to the 4K source (the 'main viewer got stuck'
report).

crates/oak-node/src/footage.rs

@@ -25,6 +25,13 @@ use crate::input::Input;
 use crate::node::{Category, NodeBehavior, NodeCore};
 use crate::value::{AudioParams, NodeValue, NodeValueRow, NodeValueTable, ValueType, VideoParams};
 
+/// Whether the footage's proxy state value means "the proxy file is
+/// ready on disk" (the C++ `ProxyState::Ready` = 2; the footage behavior
+/// stores it raw to avoid a codec-crate dependency here).
+pub(crate) fn proxymanager_proxy_state_ready(state: i32) -> bool {
+	state == 2
+}
+
 /// One media stream inside a footage file.
 #[derive(Clone, Debug)]
 pub struct StreamInfo {
@@ -364,9 +371,28 @@ impl NodeBehavior for FootageBehavior {
 		let Some(stream) = self.streams.iter().find(|s| s.is_video) else {
 			return;
 		};
+		// Proxy selection mirrors the montage path's
+		// `preview_footage_media`: enabled + Ready state, and the proxy
+		// replaces the first video stream only (C++ matches the proxy's
+		// video stream index against the footage's first video stream).
+		// `proxy_video_stream_index == -1` (a proxy generated before the
+		// stream index was recorded) still matches the FIRST video stream
+		// — a strict equality would silently disable the proxy and decode
+		// the 4K original again (the "preview stopped moving" report).
+		let proxy_ready = proxymanager_proxy_state_ready(self.proxy_state);
+		let use_proxy = self.proxy_enabled
+			&& !self.proxy.is_empty()
+			&& proxy_ready
+			&& (self.proxy_video_stream_index == stream.index
+				|| self.proxy_video_stream_index < 0);
+		let (filename, stream_index) = if use_proxy {
+			(self.proxy.clone(), 0)
+		} else {
+			(self.filename.clone(), stream.index)
+		};
 		let payload = crate::nodes::jobs::FootageJobPayload {
-			filename: self.filename.clone(),
-			stream_index: stream.index,
+			filename,
+			stream_index,
 			time,
 		};
 		table.push(