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/mod.rs

@@ -0,0 +1,88 @@
+//! Stream label extraction from BD-J disc files.
+//!
+//! Searches the disc UDF filesystem for known config files that contain
+//! stream labels (language, purpose, codec, forced flags). Four formats
+//! supported, tried in order:
+//!
+//! 1. `language_streams.txt` — Warner CTRM CSV format
+//! 2. `menu_base.prop` — Warner CTRM properties format
+//! 3. `streamproperties.xml` + `playbackconfig.xml` — Criterion XML format
+//! 4. `bluray_project.bin` — Pixelogic binary format
+
+mod language_streams;
+mod menu_base;
+mod stream_properties;
+mod bluray_project;
+
+use crate::drive::DriveSession;
+use crate::udf::UdfFs;
+
+/// A stream label extracted from disc config files.
+#[derive(Debug, Clone)]
+pub struct StreamLabel {
+    /// STN index (1-based)
+    pub stream_number: u16,
+    /// Audio or Subtitle
+    pub stream_type: StreamLabelType,
+    /// ISO 639-2 language code
+    pub language: String,
+    /// Display name (e.g. "AudioEnglishDolby", "English Dolby Atmos")
+    pub name: String,
+    /// Stream purpose
+    pub purpose: LabelPurpose,
+    /// Additional qualifier
+    pub qualifier: LabelQualifier,
+    /// Codec hint from config (e.g. "MLP", "AC3", "atmos")
+    pub codec_hint: String,
+    /// Regional variant (e.g. "US", "UK", "CF", "CS")
+    pub region: String,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum StreamLabelType {
+    Audio,
+    Subtitle,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum LabelPurpose {
+    /// Normal dialogue track
+    Normal,
+    /// Audio commentary
+    Commentary,
+    /// Descriptive audio (visually impaired)
+    Descriptive,
+    /// Music score only
+    Score,
+    /// In-movie experience
+    Ime,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum LabelQualifier {
+    None,
+    /// Subtitles for deaf and hard of hearing
+    Sdh,
+    /// Descriptive service
+    DescriptiveService,
+    /// Forced/narrative subtitle
+    Forced,
+}
+
+/// Try all parsers in order, return first successful result.
+pub fn extract(session: &mut DriveSession, udf: &UdfFs) -> Vec<StreamLabel> {
+    // Try each format in order
+    if let Some(labels) = language_streams::parse(session, udf) {
+        return labels;
+    }
+    if let Some(labels) = menu_base::parse(session, udf) {
+        return labels;
+    }
+    if let Some(labels) = stream_properties::parse(session, udf) {
+        return labels;
+    }
+    if let Some(labels) = bluray_project::parse(session, udf) {
+        return labels;
+    }
+    Vec::new()
+}