feat: initialise workspace — Milestone 1 asset explorer

Three-crate Cargo workspace structured per PROJECT.md spec:
- crates/sylpheed-formats  — Xbox 360 format parsers (no Bevy)
- crates/sylpheed-viewer   — Bevy 0.15 asset viewer + egui UI
- crates/sylpheed-cli      — CLI tools (extract/list/sniff/texture)

Milestone 1 features:
- XISO disc image reading via xdvdfs 0.8
- XPR2 texture container parsing + Morton de-tiling
- D3DFORMAT → wgpu TextureFormat mapping (DXT1/3/5, DXN, ARGB)
- Custom Bevy AssetLoader for .xpr files
- Orbit camera (LMB orbit, RMB pan, scroll zoom)
- egui file browser + RE notes panel
- CLI: extract / list / sniff / texture info / texture export
- GitHub Actions CI (Linux, macOS, Windows, WASM)
- Trunk WASM build config

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/sylpheed-formats/src/audio.rs

@@ -0,0 +1,85 @@
+//! Audio format parsing — XMA and XWB handling.
+//!
+//! Xbox 360 games use **XMA** (Xbox Media Audio) as their primary audio codec.
+//! XMA is a proprietary Microsoft codec derived from WMA Pro.
+//!
+//! ## The Challenge
+//! XMA decoding requires Microsoft's proprietary XMA decoder, which is only
+//! available in the Windows DirectX runtime. There are two approaches:
+//!
+//! ### Option A: Convert on extraction (recommended for Milestone 1)
+//! Use `xma2encode.exe` (from Xbox 360 SDK) or `ffmpeg` (has partial XMA support)
+//! to pre-convert all audio to OGG/WAV during the extraction step.
+//!
+//! ```bash
+//! # Convert a single XMA file to WAV using ffmpeg
+//! ffmpeg -i audio.xma output.wav
+//!
+//! # Or use VGMStream's test.exe for more accurate XMA decoding
+//! ```
+//!
+//! ### Option B: XMA2 software decoder
+//! The `xma2dec` project provides an open-source XMA2 decoder.
+//! GitHub: https://github.com/koolkdev/xmalib (research-quality)
+//!
+//! ### XWB Wave Bank format
+//! Xbox 360 games typically bundle audio into XWB (Xbox Wave Bank) files.
+//! These are containers that hold multiple XMA streams.
+//! Reference: https://github.com/microsoft/DirectXTK/tree/main/Audio
+
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum AudioError {
+    #[error("Unknown audio format magic: {0:?}")]
+    UnknownMagic([u8; 4]),
+    #[error("XMA decoding requires pre-conversion. See audio.rs for instructions.")]
+    XmaNotSupported,
+    #[error("Parse error: {0}")]
+    Parse(String),
+}
+
+/// An audio clip decoded to raw PCM, ready for Bevy's audio system.
+#[derive(Debug, Clone)]
+pub struct GameAudio {
+    /// Raw PCM samples (interleaved for stereo: L R L R ...)
+    pub samples: Vec<f32>,
+    pub channels: u16,
+    pub sample_rate: u32,
+}
+
+impl GameAudio {
+    /// Parse audio from raw bytes.
+    ///
+    /// Currently only WAV/PCM is supported. For XMA files, pre-convert using:
+    /// `ffmpeg -i file.xma file.wav`
+    pub fn from_bytes(bytes: &[u8]) -> Result<Self, AudioError> {
+        // Check for WAV magic
+        if bytes.len() >= 4 && &bytes[..4] == b"RIFF" {
+            return Self::from_wav(bytes);
+        }
+
+        // XMA magic bytes
+        if bytes.len() >= 4 && (
+            &bytes[..4] == b"XWB\0" || // Wave bank
+            &bytes[..4] == b"XMA2"     // Raw XMA2
+        ) {
+            return Err(AudioError::XmaNotSupported);
+        }
+
+        Err(AudioError::UnknownMagic(
+            bytes[..4.min(bytes.len())].try_into().unwrap_or([0u8; 4])
+        ))
+    }
+
+    fn from_wav(bytes: &[u8]) -> Result<Self, AudioError> {
+        // Minimal WAV parser for PCM files
+        // A proper implementation should use the `hound` crate:
+        // https://crates.io/crates/hound
+        //
+        // TODO: Add `hound = "3"` to Cargo.toml and implement properly
+        Err(AudioError::Parse(
+            "WAV parsing TODO: add `hound` crate and implement".to_string()
+        ))
+    }
+}