Preserve external subtitle language names

Summary

Fixed the subtitle menu naming path for externally attached VLC subtitle tracks. Generic VLC names like Track 2 now receive Dreamio's preserved OpenSubtitles display name when available.

Changes Made

• Changed VLC subtitle display-name reconciliation so saved external subtitle names are only consumed by generic VLC track labels.
• Expanded subtitle language-code aliases for the ISO-639-2 codes observed in Stremio/OpenSubtitles payloads, including Dutch, Danish, Romanian, Serbian, Persian, Portuguese, Finnish, Hebrew, Hungarian, Turkish, Czech, Arabic, Greek, French, German, Spanish, and English.
• Added regression coverage for Dutch and Danish three-letter subtitle codes.

Context

The debug log showed OpenSubtitles candidates arriving with usable language metadata, then VLC eventually surfacing external subtitle tracks as Track 2, Track 3, and similar generic names. Dreamio already had a preservation queue, but it could spend a queued display name on a VLC track that already had a meaningful title, which left later generic tracks unnamed.

Important Implementation Details

The key behavioral change is deliberately narrow: reconciliation now skips non-generic VLC subtitle names. If VLC gives a real name such as English (SDH) - [English], Dreamio keeps it. If VLC gives Track 4, Dreamio can replace it with the next preserved external subtitle display name.

The alias table turns common three-letter subtitle codes into two-letter language codes before asking Locale for localized names. This makes labels such as nld and dan become Dutch and Danish instead of raw codes.

Relevant Diff Snippets

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            .filter { $0.id >= 0 }
            .filter { !externalSubtitleBaselineTrackIDs.contains($0.id) }
            .filter { externalSubtitleDisplayNamesByTrackID[$0.id] == nil }
            .sorted { $0.id < $1.id }
            .forEach { track in
                guard !pendingExternalSubtitleDisplayNames.isEmpty else {
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            .filter { $0.id >= 0 }
            .filter { !externalSubtitleBaselineTrackIDs.contains($0.id) }
            .filter { externalSubtitleDisplayNamesByTrackID[$0.id] == nil }
            .filter { SubtitleDisplayName.isGenericLabel($0.name) }
            .sorted { $0.id < $1.id }
            .forEach { track in
                guard !pendingExternalSubtitleDisplayNames.isEmpty else {

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    ]

    private static let languageCodeAliases = [
        "eng": "en",
        "en": "en",
        "spa": "es",
        "es": "es",
        "fre": "fr",
        "fra": "fr",
        "fr": "fr"
    ]

    static func displayName(for candidate: SubtitleCandidate) -> String {
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    ]

    private static let languageCodeAliases = [
        "ara": "ar",
        "ar": "ar",
        "cze": "cs",
        "ces": "cs",
        "cs": "cs",
        "dan": "da",
        "da": "da",
        "de": "de",
        "deu": "de",
        "ell": "el",
        "el": "el",
        "eng": "en",
        "en": "en",
        "fin": "fi",
        "fi": "fi",
        "spa": "es",
        "es": "es",
        "ger": "de",
        "gre": "el",
        "heb": "he",
        "he": "he",
        "hun": "hu",
        "hu": "hu",
        "fre": "fr",
        "fra": "fr",
        "fr": "fr",
        "dut": "nl",
        "nld": "nl",
        "nl": "nl",
        "per": "fa",
        "fas": "fa",
        "fa": "fa",
        "pob": "pt",
        "por": "pt",
        "pt": "pt",
        "ron": "ro",
        "rum": "ro",
        "ro": "ro",
        "srp": "sr",
        "sr": "sr",
        "tur": "tr",
        "tr": "tr"
    ]

    static func displayName(for candidate: SubtitleCandidate) -> String {

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            )),
            "movie.es"
        )
    }

    private static func testSubtitleDisplayNameUsesPreservedNamesForGenericVLCTracks() {
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            )),
            "movie.es"
        )
        assertEqual(
            SubtitleDisplayName.displayName(for: SubtitleCandidate(
                url: URL(string: "https://opensubtitles.example.test/download/subtitle.srt")!,
                label: "Track 3",
                language: "nld"
            )),
            "Dutch"
        )
        assertEqual(
            SubtitleDisplayName.displayName(for: SubtitleCandidate(
                url: URL(string: "https://opensubtitles.example.test/download/subtitle.srt")!,
                label: "Track 4",
                language: "dan"
            )),
            "Danish"
        )
    }

    private static func testSubtitleDisplayNameUsesPreservedNamesForGenericVLCTracks() {

Expected Impact for End-Users

When subtitles load through the native VLC player, the captions menu should be easier to scan. Users should see language names for generic external subtitle tracks instead of guessing which Track N corresponds to the language they want.

Validation

• Ran swiftc -parse-as-library Dreamio/StreamCandidate.swift Dreamio/StreamResolver.swift Tests/StreamResolverTests.swift -o /tmp/StreamResolverTests && /tmp/StreamResolverTests: passed.
• Ran DEVELOPER_DIR=/Applications/Xcode.app/Contents/Developer xcodebuild -workspace Dreamio.xcworkspace -scheme Dreamio -configuration Debug -sdk iphonesimulator build: passed.

Issues, Limitations, and Mitigations

This still depends on VLC eventually surfacing external subtitle tracks after addPlaybackSlave. The change improves the names once tracks appear; it does not change VLC's asynchronous attachment behavior or guarantee that every remote subtitle file becomes visible instantly.

Follow-up Work

No required follow-up remains for this fix. A useful later improvement would be deeper URL-to-track correlation if MobileVLCKit exposes enough metadata to map each external subtitle slave to an exact surfaced track.