fix(wzp-video): cfg-gate dav1d + svt-av1 off Android target

shiguredo_dav1d and shiguredo_svt_av1 build scripts panic with
'unsupported target: os=android, arch=aarch64'. The AV1 SW fallback
is only needed on macOS / Linux desktop — Android uses MediaCodec
for AV1 anyway.

- Cargo.toml: AV1 SW deps moved under cfg(not(target_os = "android"))
- lib.rs: cfg-gate the dav1d and svt_av1 modules and re-exports
- factory.rs: on Android, Av1Main paths return NotInitialized when
  HW MediaCodec is also unavailable (only path on Android)
- factory tests: assert NotInitialized on Android, Ok elsewhere

Unblocks T4.3.1.1 (Android target-compile of wzp-video / mediacodec).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/wzp-video/Cargo.toml

@@ -7,11 +7,15 @@ rust-version.workspace = true
 
 [dependencies]
 bytes = { workspace = true }
-shiguredo_dav1d = "2026.1.0"
-shiguredo_svt_av1 = "2026.1.0"
 tracing = { workspace = true }
 wzp-proto = { path = "../wzp-proto" }
 
+# AV1 SW codecs do not support Android target (build.rs panics on
+# aarch64-linux-android). Android uses MediaCodec for AV1 instead.
+[target.'cfg(not(target_os = "android"))'.dependencies]
+shiguredo_dav1d = "2026.1.0"
+shiguredo_svt_av1 = "2026.1.0"
+
 [target.'cfg(target_os = "macos")'.dependencies]
 shiguredo_video_toolbox = "2026.1"
 

crates/wzp-video/src/factory.rs

@@ -68,12 +68,21 @@ pub fn create_video_encoder(
             }
         }
         CodecId::Av1Main => {
-            // SVT-AV1 is the universal SW fallback.
-            // macOS VideoToolbox has no AV1 encode. Android MediaCodec AV1
-            // encode requires API 29+ and may not be available on all devices.
+            // SVT-AV1 is the universal SW fallback for non-Android targets.
+            // On Android, MediaCodec AV1 (`video/av01`) is the only available
+            // path — shiguredo_svt_av1 does not build for aarch64-linux-android.
             let _ = bitrate_bps; // SvtAv1Encoder currently hard-codes bitrate
+            #[cfg(target_os = "android")]
+            {
+                let _ = (width, height);
+                #[allow(clippy::needless_return)]
+                return Err(VideoError::NotInitialized);
+            }
+            #[cfg(not(target_os = "android"))]
+            {
                 Ok(Box::new(crate::svt_av1::SvtAv1Encoder::new(width, height)?))
             }
+        }
         _ => Err(VideoError::InvalidInput("not a video codec".into())),
     }
 }
@@ -131,7 +140,9 @@ pub fn create_video_decoder(
             }
         }
         CodecId::Av1Main => {
-            // Try platform HW decoders first, then fall back to dav1d.
+            // Try platform HW decoders first, then fall back to dav1d on
+            // non-Android targets. On Android, MediaCodec is the only path —
+            // shiguredo_dav1d does not build for aarch64-linux-android.
             #[cfg(target_os = "macos")]
             {
                 if let Ok(dec) = crate::videotoolbox::VideoToolboxAv1Decoder::new(width, height) {
@@ -140,12 +151,14 @@ pub fn create_video_decoder(
             }
             #[cfg(target_os = "android")]
             {
-                if let Ok(dec) = crate::mediacodec::MediaCodecAv1Decoder::new(width, height) {
-                    return Ok(Box::new(dec));
-                }
+                return crate::mediacodec::MediaCodecAv1Decoder::new(width, height)
+                    .map(|d| Box::new(d) as Box<dyn VideoDecoder>);
             }
+            #[cfg(not(target_os = "android"))]
+            {
                 Ok(Box::new(crate::dav1d::Dav1dDecoder::new()?))
             }
+        }
         _ => Err(VideoError::InvalidInput("not a video codec".into())),
     }
 }
@@ -157,18 +170,30 @@ mod tests {
     #[test]
     fn av1_encoder_factory_creates_svt_av1() {
         let enc = create_video_encoder(CodecId::Av1Main, 640, 480, 2_000_000);
+        #[cfg(target_os = "android")]
+        assert!(
+            matches!(enc, Err(VideoError::NotInitialized)),
+            "AV1 SW encoder is unavailable on Android (no shiguredo_svt_av1)"
+        );
+        #[cfg(not(target_os = "android"))]
         assert!(
             enc.is_ok(),
-            "AV1 encoder factory should succeed on all platforms"
+            "AV1 encoder factory should succeed on non-Android platforms"
         );
     }
 
     #[test]
     fn av1_decoder_factory_creates_decoder() {
         let dec = create_video_decoder(CodecId::Av1Main, 640, 480);
+        #[cfg(target_os = "android")]
+        assert!(
+            matches!(dec, Err(VideoError::NotInitialized)),
+            "AV1 decoder requires MediaCodec on Android; non-Android device returns NotInitialized"
+        );
+        #[cfg(not(target_os = "android"))]
         assert!(
             dec.is_ok(),
-            "AV1 decoder factory should succeed on all platforms"
+            "AV1 decoder factory should succeed on non-Android (dav1d SW fallback)"
         );
     }
 

crates/wzp-video/src/lib.rs

@@ -6,6 +6,7 @@
 
 pub mod av1_obu;
 pub mod controller;
+#[cfg(not(target_os = "android"))]
 pub mod dav1d;
 pub mod decoder;
 pub mod depacketizer;
@@ -16,11 +17,13 @@ pub mod framer;
 pub mod mediacodec;
 pub mod nack;
 pub mod simulcast;
+#[cfg(not(target_os = "android"))]
 pub mod svt_av1;
 pub mod videotoolbox;
 
 pub use av1_obu::{Av1Depacketizer, Av1ObuFramer, is_keyframe_obu};
 pub use controller::{VideoQualityController, VideoTarget};
+#[cfg(not(target_os = "android"))]
 pub use dav1d::Dav1dDecoder;
 pub use decoder::VideoDecoder;
 pub use depacketizer::H264Depacketizer;
@@ -34,6 +37,7 @@ pub use mediacodec::{
 };
 pub use nack::{CachedPacket, NackAction, NackReceiver, NackSender};
 pub use simulcast::{LayerPacket, LayerTarget, SimulcastEncoder, SimulcastLayer};
+#[cfg(not(target_os = "android"))]
 pub use svt_av1::SvtAv1Encoder;
 pub use videotoolbox::{
     VideoToolboxAv1Decoder, VideoToolboxDecoder, VideoToolboxEncoder, VideoToolboxHevcDecoder,