refactor: 删除部分多余的代码和注释

src/stream_encoder.rs

@@ -0,0 +1,18 @@
+//! `EncoderType` → `EncoderBackend` (breaks config ↔ video import cycles).
+
+use crate::config::EncoderType;
+use crate::video::encoder::EncoderBackend;
+
+/// `None` means “auto” in WebRTC / pipeline (same as `EncoderType::Auto`).
+pub fn encoder_type_to_backend(encoder: EncoderType) -> Option<EncoderBackend> {
+    match encoder {
+        EncoderType::Auto => None,
+        EncoderType::Software => Some(EncoderBackend::Software),
+        EncoderType::Vaapi => Some(EncoderBackend::Vaapi),
+        EncoderType::Nvenc => Some(EncoderBackend::Nvenc),
+        EncoderType::Qsv => Some(EncoderBackend::Qsv),
+        EncoderType::Amf => Some(EncoderBackend::Amf),
+        EncoderType::Rkmpp => Some(EncoderBackend::Rkmpp),
+        EncoderType::V4l2m2m => Some(EncoderBackend::V4l2m2m),
+    }
+}