[WIP] Audio codec probe/detection + CLI audio-info + viewer audio panel

Snapshot of local WIP before rebasing onto the movie/voice remote work.
- audio.rs: AudioCodec enum, AudioInfo::probe (RIFF/WAVE parse, raw-XMA2
  Shannon-entropy heuristic looks_like_raw_xma2), from_wav, riff_data_span.
- cli/main.rs: `audio-info` subcommand (cmd_audio_info).
- viewer ui.rs/iso_loader.rs: draw_audio_detail panel wiring.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/sylpheed-cli/src/main.rs

@@ -103,6 +103,21 @@ enum Commands {
         #[command(subcommand)]
         cmd: MeshCommands,
     },
+
+    /// Audio tools (identify WAV/XMA/XMA2 + metadata)
+    Audio {
+        #[command(subcommand)]
+        cmd: AudioCommands,
+    },
+}
+
+#[derive(Subcommand)]
+enum AudioCommands {
+    /// Identify an audio file/stream and print its metadata
+    Info {
+        /// Path to a WAV / XMA / raw audio stream
+        file: PathBuf,
+    },
 }
 
 #[derive(Subcommand)]
@@ -202,9 +217,41 @@ async fn main() -> Result<()> {
             PakCommands::List { pak, idxd_only } => cmd_pak_list(&pak, idxd_only),
             PakCommands::Dump { pak, hash }      => cmd_pak_dump(&pak, &hash),
         },
+        Commands::Audio { cmd } => match cmd {
+            AudioCommands::Info { file } => cmd_audio_info(&file),
+        },
     }
 }
 
+// ── audio info ───────────────────────────────────────────────────────────────
+
+fn cmd_audio_info(file: &Path) -> Result<()> {
+    use sylpheed_formats::AudioInfo;
+    let bytes = std::fs::read(file).with_context(|| format!("Cannot read {}", file.display()))?;
+    let info = AudioInfo::probe(&bytes);
+
+    println!("{} {}", "Audio:".green().bold(), file.display());
+    println!("  Codec      : {}", info.codec.label().yellow());
+    let opt = |v: Option<String>| v.unwrap_or_else(|| "—".dimmed().to_string());
+    println!("  Channels   : {}", opt(info.channels.map(|c| c.to_string())));
+    println!("  Sample rate: {}", opt(info.sample_rate.map(|r| format!("{r} Hz"))));
+    println!("  Bit depth  : {}", opt(info.bits_per_sample.map(|b| format!("{b}-bit"))));
+    if let Some(d) = info.duration_secs {
+        println!("  Duration   : {d:.2} s");
+    }
+    if let Some(p) = info.xma_packets {
+        println!("  XMA packets: {} (2048 B each)", p.to_string().yellow());
+    }
+    println!("  Size       : {} bytes", info.size_bytes.to_string().yellow());
+    if info.codec.needs_decoder() {
+        println!(
+            "  {} decode not supported (needs an XMA2 decoder + the sound-bank descriptor)",
+            "note:".dimmed()
+        );
+    }
+    Ok(())
+}
+
 // ── extract ────────────────────────────────────────────────────────────────
 
 async fn cmd_extract(iso_path: &Path, output_dir: &Path) -> Result<()> {