test(oak-codec, oak-core): boundary and branch coverage

Fixture-backed unit and contract tests for FFmpeg helpers and state
machines, OCIO color factories, wgpu backend fallbacks, and the safe
parts of the platform import module (review report section 10.2).

crates/oak-codec/src/proxymanager.rs

@@ -769,4 +769,86 @@ mod tests_extra {
 		);
 	}
 }
- 		);
+
+#[cfg(test)]
+mod tests_coverage {
+	use super::*;
+
+	#[test]
+	fn proxy_state_numeric_and_string_conversions() {
+		assert_eq!(ProxyState::try_from(0), Ok(ProxyState::Missing));
+		assert_eq!(ProxyState::try_from(1), Ok(ProxyState::Generating));
+		assert_eq!(ProxyState::try_from(2), Ok(ProxyState::Ready));
+		assert_eq!(ProxyState::try_from(3), Ok(ProxyState::Failed));
+		assert_eq!(ProxyState::try_from(4), Err(()));
+		assert_eq!(ProxyState::try_from(-1), Err(()));
+
+		for state in [
+			ProxyState::Missing,
+			ProxyState::Generating,
+			ProxyState::Ready,
+			ProxyState::Failed,
+		] {
+			let name = ProxyManager::proxy_state_to_string(state);
+			assert_eq!(ProxyManager::proxy_state_from_string(&name), state);
+			assert_eq!(
+				ProxyManager::proxy_state_from_string(&(state as i32).to_string()),
+				state
+			);
+		}
+
+		// Whitespace is trimmed; unknown names fall back to Missing.
+		assert_eq!(
+			ProxyManager::proxy_state_from_string("  generating "),
+			ProxyState::Generating
+		);
+		assert_eq!(
+			ProxyManager::proxy_state_from_string("bogus"),
+			ProxyState::Missing
+		);
+		assert_eq!(ProxyManager::proxy_state_from_string(""), ProxyState::Missing);
+	}
+
+	#[test]
+	fn proxy_filename_audio_tag_detection() {
+		assert!(ProxyManager::proxy_filename_has_audio("/c/shot.a1.mp4"));
+		assert!(ProxyManager::proxy_filename_has_audio("shot.a1.mov"));
+		assert!(!ProxyManager::proxy_filename_has_audio("/c/shot.a2.mp4"));
+		assert!(!ProxyManager::proxy_filename_has_audio("/c/shot.mp4"));
+		assert!(!ProxyManager::proxy_filename_has_audio(""));
+	}
+
+	#[test]
+	fn get_proxy_state_reads_the_filesystem() {
+		assert_eq!(ProxyManager::get_proxy_state(""), ProxyState::Missing);
+
+		let dir = std::env::temp_dir().join(format!("oakcodec-proxy-coverage-{}", std::process::id()));
+		std::fs::create_dir_all(&dir).unwrap();
+
+		// A finished proxy exists on disk.
+		let proxy = dir.join("clip.mp4");
+		std::fs::write(&proxy, b"proxy").unwrap();
+		assert_eq!(
+			ProxyManager::get_proxy_state(&proxy.to_string_lossy()),
+			ProxyState::Ready
+		);
+
+		// Only the working file exists: still generating.
+		let pending = dir.join("pending.mp4");
+		let working =
+			ProxyManager::get_working_filename(&pending.to_string_lossy()).unwrap();
+		std::fs::write(&working, b"partial").unwrap();
+		assert_eq!(
+			ProxyManager::get_proxy_state(&pending.to_string_lossy()),
+			ProxyState::Generating
+		);
+
+		// Neither file exists.
+		assert_eq!(
+			ProxyManager::get_proxy_state(&dir.join("none.mp4").to_string_lossy()),
+			ProxyState::Missing
+		);
+
+		std::fs::remove_dir_all(&dir).ok();
+	}
+}