refactor: clear too_many_arguments and large_enum_variant warnings

Oracle P2 batch 2 (refactor items). Drops both remaining design-shape
clippy warnings to zero without behavior change.

  - avhw.rs build_filter_graph: drop unused _enc_width/_enc_height params
    (Oracle caught them during P2 review — passed by EncState::new but
    never read inside the function; the filter graph uses width/height
    only). Signature: 8 args -> 6 args (under clippy's 7 threshold).

  - state.rs InFlightSurface::CopyQueued: Box the drm_map field.
    AVDRMFrameDescriptor is ~592 bytes (4 objects + 4 layers); the enum
    size was being dominated by this variant, ballooning every
    InFlightSurface value to 592 bytes even for the None/AllocQueued
    variants. Box<AVDRMFrameDescriptor> shrinks the enum to ~32 bytes
    regardless of variant. The drm_map field is currently destructured
    under _drm_map (unused), so the boxing has no consumer-side impact.

  - state_portal.rs webrtc_thread_loop: 10 args -> 4 args via two new
    structs:
      * WebRtcThreadConfig { fps, enc_width, enc_height, max_bitrate }
        — immutable for the thread's lifetime; a tier change spawns a
        new thread rather than mutating.
      * WebRtcThreadChannels { webrtc_rx, sent_gap_tx, bitrate_tx,
        resolution_tx } — channel endpoints owned exclusively by the
        sender thread after spawn.
    wrtc (WebRtcState) and paused (Arc<AtomicBool>) stay as separate
    args because they have different ownership semantics (moved-in
    state vs shared atomic). Documented as doc comments on the new
    types so the next reader understands the bundle rationale.

All 79 unit tests + 3 integration tests pass. clippy: 0 errors.
Per-file warning counts: state_portal.rs down from 3 to 0; state.rs
down from 8 to 4 (remaining are unrelated dead-code on OutputInfo /
starting_timestamp).

src/state_portal.rs

@@ -42,6 +42,26 @@ struct WebrtcThread {
     sent_gap_rx: crossbeam_channel::Receiver<(f64, Option<f64>)>,
 }
 
+/// Static configuration handed to the WebRTC sender thread. Immutable for the
+/// thread's lifetime; a resolution tier change rebuilds the whole pipeline
+/// (and spawns a new thread) rather than mutating this.
+struct WebRtcThreadConfig {
+    fps: u32,
+    enc_width: u32,
+    enc_height: u32,
+    max_bitrate: u64,
+}
+
+/// Channel endpoints owned exclusively by the WebRTC sender thread after spawn.
+/// The reverse endpoints stay with StatePortal (or the encode thread) for
+/// inbound/outbound traffic.
+struct WebRtcThreadChannels {
+    webrtc_rx: crossbeam_channel::Receiver<EncodedH264Frame>,
+    sent_gap_tx: crossbeam_channel::Sender<(f64, Option<f64>)>,
+    bitrate_tx: crossbeam_channel::Sender<BitrateCommand>,
+    resolution_tx: crossbeam_channel::Sender<BitrateCommand>,
+}
+
 /// 门户模式的主状态机
 ///
 /// 负责管理从 PipeWire 采集屏幕帧、通过 VAAPI 硬件编码的完整生命周期。
@@ -288,15 +308,19 @@ impl StatePortal {
                         .spawn(move || {
                             webrtc_thread_loop(
                                 wrtc,
-                                webrtc_rx,
-                                fps,
-                                enc_width,
-                                enc_height,
-                                max_bitrate,
+                                WebRtcThreadConfig {
+                                    fps,
+                                    enc_width,
+                                    enc_height,
+                                    max_bitrate,
+                                },
+                                WebRtcThreadChannels {
+                                    webrtc_rx,
+                                    sent_gap_tx,
+                                    bitrate_tx,
+                                    resolution_tx,
+                                },
                                 paused,
-                                sent_gap_tx,
-                                bitrate_tx,
-                                resolution_tx,
                             )
                         })?;
                     self.webrtc_thread = Some(WebrtcThread {
@@ -695,16 +719,22 @@ fn encode_thread_loop(
 
 fn webrtc_thread_loop(
     mut wrtc: WebRtcState,
-    webrtc_rx: crossbeam_channel::Receiver<EncodedH264Frame>,
-    fps: u32,
-    enc_width: u32,
-    enc_height: u32,
-    max_bitrate: u64,
+    config: WebRtcThreadConfig,
+    channels: WebRtcThreadChannels,
     paused: Arc<AtomicBool>,
-    sent_gap_tx: crossbeam_channel::Sender<(f64, Option<f64>)>,
-    bitrate_tx: crossbeam_channel::Sender<BitrateCommand>,
-    resolution_tx: crossbeam_channel::Sender<BitrateCommand>,
 ) {
+    let WebRtcThreadConfig {
+        fps,
+        enc_width,
+        enc_height,
+        max_bitrate,
+    } = config;
+    let WebRtcThreadChannels {
+        webrtc_rx,
+        sent_gap_tx,
+        bitrate_tx,
+        resolution_tx,
+    } = channels;
     let mut frames_sent: u64 = 0;
     let mut last_send: Option<std::time::Instant> = None;
     let mut last_sent_bitrate: Option<u64> = None;