feat(player): opt-in stream information caption with playlist name

[bilipp]

What

Brings an in-player stream information caption to iOS, iPadOS, macOS and visionOS, shows the owning playlist's name in it, and adds a Simple / Advanced detail-level preference.

Until now the only information surface in the app was the tvOS player chrome — TVPlayerControlsOverlay.titleBlock and the Info panel, every file behind them wrapped in #if os(tvOS). The four non-tvOS engine overlays rendered only title, subtitle and a LIVE dot. So this builds one shared leaf rather than flipping a gate.

Simple

Example · NEWS

Advanced

Example · NEWS · 1080p · H264 · 24 fps · KSPlayer

Settings (Player section, free, no paywall)

Stream Information
  Show Stream Information          [OFF]
  Detail Level                  Simple ⌄
  Shows the playlist, category, and what's on now.

Design decisions

• Rides the existing controls and inherits their auto-hide. No new button, panel or gesture — the tap-to-toggle, the scrubber drag, the interactive fullScreenCover dismiss and macOS .onContinuousHover already compete on that surface. (tvOS's "show it briefly on channel change" has no iOS equivalent: switchLiveChannel / LiveChannelNavigator exist only inside #if os(tvOS).)
• Off by default, free for everyone.
• One shared leaf mounted from all four engine overlays, the way PlayerEpisodeOverlays already is — never four inline edits to four near-identical title blocks. tvOS and non-tvOS both derive from the same PlayerInfoSnapshot, so they cannot drift.
• tvOS defaults to Advanced, so its caption is unchanged apart from the added playlist name. It gains the same Detail Level picker in its player settings pane.
• The playlist is the one that owns the item, recovered from the content id's UUID prefix with a single predicated fetchLimit = 1 fetch. Not the globally selected playlist — that would be actively wrong for cross-playlist search, the Other Sources rail, Downloads, Continue Watching and lume://play deep links. No ?? playlists.first fallback: a miss collapses the row.
• No schema change, and no new field on PlayableMedia — it is Codable, is the macOS WindowGroup value and is JSON-persisted by PlaybackResumeStore for the Live Activity's lume://resume.

Two pre-existing bugs fixed on the way

• KSPlayer, the default engine, had no videoInfo off tvOS. Its only producer lived in the tvOS-gated KSTVPlaybackEngine.refreshVideoInfo(). Lifted verbatim into an ungated KSVideoInfo that both platforms now call — otherwise the Advanced readout would be permanently blank for most users.
• PlayerVideoInfo.captionParts hardcoded "… fps" and String(format: "%.2f") — untranslated, and a period decimal separator that is wrong in de/fr/es/pt/it. Now localized and locale-aware, with the English rendering unchanged.

Graceful degradation

Elements with no value collapse rather than emitting a dangling separator — the common case, since AVPlayer reports fps: 0, codec: nil (and an active AirPlay route silently forces AVPlayer), and a live channel with no matched XMLTV has no programme. Covered by tests.

Performance

Preferences are device-local UserDefaults read directly, with @AppStorage only in the leaf — hoisting it into an engine view or FullScreenPlayerView would re-render the whole player tree on every toggle. The per-stream resolve hangs off the same enabled gate, so a viewer with the caption off pays for no fetch at all. EPG comes from ChannelEPGLoader off-main, never a @Query<EPGListing>.

Verification

Builds	iOS ✅ · iPadOS ✅ · tvOS ✅ · macOS ✅ · visionOS ⚠️ not built
Tests	1004/1004 pass (30 new)
Lint	vendored swiftformat 0/31 need formatting; swiftlint --strict exit 0
Localization	12 new keys, all 9 locales, check-translations.swift → OK

Also verified by hand on an iPhone 17 Pro simulator against the example server: both detail levels render, the playlist name is correct, and a channel with no EPG collapses cleanly.

Reviewer notes

• visionOS is unbuilt — the platform is not installed on the machine this was developed on. The #if !os(tvOS) gate ships it there and no visionOS-specific API is involved, so the risk is layout rather than compilation, but it has not been compiled.
• Advanced truncates on iPhone portrait. The caption is one line at .caption with minimumScaleFactor(0.7), riding the control column above the transport; with every Advanced element the engine name gets clipped. Fine in landscape and on iPad/Mac. Worth deciding separately whether Advanced should drop the engine name on compact widths.
• Dynamic Type is clamped at accessibility1 — above that the caption crowds the title and scrubber off the video. VoiceOver still reads the full expanded label ("24 frames per second", not "24 f p s") as a single element regardless of rendered size.
• .gitignore gains a bare ExampleData line; the existing ExampleData/ does not match the symlink a worktree needs.