Add labels module: 4 disc file parsers for stream labels

src/labels/ with 4 parsers tried in order:
1. language_streams.txt (Warner CTRM CSV)
2. menu_base.prop (Warner CTRM properties)
3. streamproperties.xml + playbackconfig.xml (Criterion XML)
4. bluray_project.bin (Pixelogic binary tokens)

Disc::scan() calls labels::extract() → apply_disc_labels().
If no disc files found, streams keep MPLS data as-is.
No JAR fallback — disc files or nothing.

Covers 4/8 discs with JARs (Dunkirk UHD, V for Vendetta BD,
Being There, Barbie). Remaining 3 (Civil War, Dune, V for
Vendetta UHD) have no disc config files.

src/labels/language_streams.rs

@@ -0,0 +1,88 @@
+//! Parser for `language_streams.txt` — Warner CTRM CSV format.
+//!
+//! Found at: `BDMV/JAR/*/language_streams.txt`
+//!
+//! Format:
+//! ```text
+//! playlist_id, type, stream_num, language, variant
+//! 100, audio_production, 1, eng, atmos
+//! 100, subtitle_narrative, 7, fra,
+//! ```
+
+use crate::drive::DriveSession;
+use crate::udf::{UdfFs, DirEntry};
+use super::{StreamLabel, StreamLabelType, LabelPurpose, LabelQualifier};
+
+pub fn parse(session: &mut DriveSession, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+    // Search BDMV/JAR/*/ for language_streams.txt
+    let jar_dir = udf.find_dir("/BDMV/JAR")?;
+    let data = find_and_read(session, udf, jar_dir, "language_streams.txt")?;
+    let text = std::str::from_utf8(&data).ok()?;
+
+    let mut labels = Vec::new();
+
+    for line in text.lines() {
+        let line = line.trim();
+        if line.is_empty() || line.starts_with('#') { continue; }
+
+        let parts: Vec<&str> = line.split(',').map(|s| s.trim()).collect();
+        if parts.len() < 4 { continue; }
+
+        let _playlist_id = parts[0]; // could filter by playlist later
+        let type_str = parts[1];
+        let stream_num: u16 = match parts[2].parse() {
+            Ok(n) => n,
+            Err(_) => continue,
+        };
+        let language = parts[3].to_string();
+        let variant = if parts.len() > 4 { parts[4].to_string() } else { String::new() };
+
+        let (stream_type, purpose, qualifier) = match type_str {
+            "audio_production" => (StreamLabelType::Audio, LabelPurpose::Normal, LabelQualifier::None),
+            "audio_commentary" => (StreamLabelType::Audio, LabelPurpose::Commentary, LabelQualifier::None),
+            "audio_ime" => (StreamLabelType::Audio, LabelPurpose::Ime, LabelQualifier::None),
+            "subtitle_production" => (StreamLabelType::Subtitle, LabelPurpose::Normal, LabelQualifier::None),
+            "subtitle_commentary" => (StreamLabelType::Subtitle, LabelPurpose::Commentary, LabelQualifier::None),
+            "subtitle_narrative" => (StreamLabelType::Subtitle, LabelPurpose::Normal, LabelQualifier::Forced),
+            "subtitle_dual" => (StreamLabelType::Subtitle, LabelPurpose::Normal, LabelQualifier::None),
+            "subtitle_bonus" => (StreamLabelType::Subtitle, LabelPurpose::Normal, LabelQualifier::None),
+            "subtitle_ime" => (StreamLabelType::Subtitle, LabelPurpose::Ime, LabelQualifier::None),
+            "subtitle_ime_narrative" => (StreamLabelType::Subtitle, LabelPurpose::Ime, LabelQualifier::Forced),
+            _ => continue,
+        };
+
+        // Skip feature_override_default lines
+        if type_str == "feature_override_default" { continue; }
+
+        let codec_hint = variant.clone(); // "atmos", "eda", etc.
+
+        labels.push(StreamLabel {
+            stream_number: stream_num,
+            stream_type,
+            language,
+            name: String::new(),
+            purpose,
+            qualifier,
+            codec_hint,
+            region: String::new(),
+        });
+    }
+
+    if labels.is_empty() { return None; }
+    Some(labels)
+}
+
+/// Search subdirectories of a parent for a file by name.
+fn find_and_read(session: &mut DriveSession, udf: &UdfFs, parent: &DirEntry, filename: &str) -> Option<Vec<u8>> {
+    for entry in &parent.entries {
+        if entry.is_dir {
+            let sub_path = format!("/BDMV/JAR/{}/{}", entry.name, filename);
+            if let Ok(data) = udf.read_file(session, &sub_path) {
+                if !data.is_empty() {
+                    return Some(data);
+                }
+            }
+        }
+    }
+    None
+}