labels: per-parser confidence + highest-confidence-wins registry

Replaces 'first-match-wins by array order' with 'highest-confidence-
wins, array order tiebreaker'. Removes the arbitrariness when more
than one parser can claim a disc (e.g. one with both
bluray_project.bin and playlists.xml).

New types in labels::mod:
  pub enum Confidence { Medium, High }
  pub struct ParseResult { labels: Vec<StreamLabel>, confidence }
  ParseResult::high(labels) / ::medium(labels) constructors

Parser signature change: every parse() now returns
Option<ParseResult> instead of Option<Vec<StreamLabel>>. Updated all
six parsers in lockstep:
  paramount: High (fully structured XML)
  criterion: High (fully structured XML)
  pixelogic: High by default, Medium when an unknown token component
             is encountered (the skip-unknown path now propagates the
             coverage gap to the caller instead of silently degrading)
  ctrm:      High (structured key-value)
  dbp:       High (anchor scan with vocab routing)
  deluxe:    still returns None pending Phase D — signature aligned

Registry behavior:
  extract() iterates all detect-positive parsers, picks highest
  Confidence with non-empty labels. Equal confidence falls to array
  order (deterministic). Same selection logic in analyze().

LabelAnalysis grew a confidence: Option<Confidence> field so the
diagnostic surface (freemkv-tools labels-analyze) exposes which
confidence tier the selected parser claimed. labels-analyze JSON
and labels-corpus-check structural diff both gained the field.

Precommit (cargo +1.86 fmt + clippy + test) green.

src/labels/criterion.rs

@@ -3,7 +3,7 @@
 //! Clean structured XML with Content/Qualifier per stream and
 //! stream number mapping via playbackconfig.
 
-use super::{LabelPurpose, LabelQualifier, StreamLabel, StreamLabelType};
+use super::{LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelType};
 use crate::sector::SectorReader;
 use crate::udf::UdfFs;
 use std::collections::HashMap;
@@ -12,7 +12,7 @@ pub fn detect(udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "streamproperties.xml")
 }
 
-pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<ParseResult> {
     let sp_data = super::read_jar_file(reader, udf, "streamproperties.xml")?;
     let sp_text = std::str::from_utf8(&sp_data).ok()?;
 
@@ -66,7 +66,8 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
     if labels.is_empty() {
         return None;
     }
-    Some(labels)
+    // High confidence: streamproperties.xml is fully structured.
+    Some(ParseResult::high(labels))
 }
 
 struct StreamInfo {