Add configurable spec compliance mode for track property validation

[TimGels]

Problem

The current UI allows setting properties that violate the Matroska specification:

Current UI Issues:

• Audio tracks show "Forced Flag" option (spec: forced applies only to subtitles)
• Video tracks show "Forced Flag" option (spec: forced applies only to subtitles)
• Subtitle tracks missing "Default Flag" option (spec: default applies to all track types)

Specification vs Implementation:

Property	Matroska Spec v4	mkvpropedit Tool
FlagDefault (0x88)	Valid for audio/subtitle/video track types	Accepts for all track types ✓
FlagForced (0x55AA)	"Applies only to subtitles"	Accepts for all track types ⚠️

References:

• Matroska Spec: https://www.matroska.org/technical/elements.html

Root Cause

mkvpropedit is intentionally permissive - it's a low-level EBML editing tool that doesn't enforce semantic rules. It allows setting any valid EBML element regardless of spec semantics.

Players ignore semantically invalid flags - Even if you set flag-forced on an audio track, players won't honor it because the spec says it only applies to subtitles.

Proposed Solution

Add a Spec Compliance Mode setting with two options:

Option 1: "Strict (Spec-Compliant)" [DEFAULT] ✅

• Follow Matroska v4 specification semantics
• Show only spec-valid properties per track type:
  • Audio: Default flag, Language, Track name, Codec
  • Video: Default flag, Language, Track name, Codec
  • Subtitle: Default flag, Forced flag, Language, Track name, Codec

Benefits:

• Guides users toward correct usage
• Produces files that players handle as expected
• Prevents confusion about why forced flags don't work on audio/video

Option 2: "Permissive (Tool-Compatible)" ⚠️

• Match mkvpropedit's capabilities exactly
• Show all properties for all track types (regardless of spec)
• For advanced users who know what they're doing

Benefits:

• Maximum flexibility
• Allows edge cases (legacy files, experimental usage)
• Matches underlying tool capabilities

UI Changes Required

1. SettingsPage.xaml - Add new setting:

   <ComboBox Header="Spec Compliance Mode">
     <ComboBoxItem Content="Strict (Spec-Compliant) [Recommended]" IsSelected="True"/>
     <ComboBoxItem Content="Permissive (Tool-Compatible)"/>
   </ComboBox>

2. Track Validation UI - Conditionally show/hide properties based on mode:

   • Audio Track section (lines 163-224): Hide "Forced Flag" in Strict mode
   • Video Track section (lines 226-268): Hide "Forced Flag" in Strict mode
   • Subtitle Track section (lines 270+): Add "Default Flag" (show in both modes)

3. Models - Add to \ValidationSettings.cs:

   public enum SpecComplianceMode
   {
       Strict,      // Spec-compliant (default)
       Permissive   // Tool-compatible
   }
   
   public SpecComplianceMode ComplianceMode { get; set; } = SpecComplianceMode.Strict;

Implementation Considerations

1. Default behavior: Strict mode should be default to guide users correctly
2. Warning text: Show info icon explaining what each mode means
3. Backward compatibility: Existing user settings remain valid in both modes
4. Validation: All existing validation rules work in both modes (they check consistency, not spec compliance)
5. Command generation: Both modes generate valid mkvpropedit commands (tool accepts both)

Scope

This is a UI/configuration enhancement only:

• ✅ Affects which properties are shown in Settings page
• ✅ Affects which validation severities user can configure
• ❌ Does NOT affect validation rules (they already work correctly)
• ❌ Does NOT affect command generation (mkvpropedit accepts both)

[TimGels]

I will first only have the "permissive" option UI available first, and in the future look into whether to implement this idea as a setting or not. The Matroska / EBML specifications are notoriously vague complicated to work with in a "spec compliant" manner. Lots of tools don't implement it "correctly" and most players just do whatever they feel is right.