Expand PlexBar into native macOS and Apple TV apps

[austin-smith]

What Changed

• Replace the SwiftPM app layout with native Xcode targets, shared schemes, build configuration, and Xcode-based macOS CI and release workflows.
• Build native macOS and tvOS Plex clients with account/device authorization, server discovery, library browsing, search, media details, and AVKit playback; retain macOS downloads and the persistent menu-bar dashboard.
• Add the Apple TV Top Shelf extension with cached artwork and server-scoped content links.
• Share playback decisions, request parameters, media selection, queue operations, chapter/marker contracts, artwork, and episode presentation across platforms. Expand Apple TV playback preferences and queue controls.
• Refine macOS fullscreen keyboard handling, stream activity summaries, visible-window refresh scheduling, and session-event reconciliation; add regression coverage and platform documentation.

Why

PlexBar had outgrown its SwiftPM utility structure. This overhaul establishes native Mac and Apple TV clients and shares Plex contracts and presentation rules while preserving platform-native browsing and playback controls.

UI Changes

• Add the macOS main-window library, search, cinematic media details, people, downloads, and inline player alongside the menu-bar dashboard.
• Add Apple TV Home, Libraries, Search, Settings, remote-driven detail and season browsing, native player menus, and Top Shelf content.
• Align artwork, episode labels, metadata, and watched states, and show activity totals and stale/error states in the Mac window and menu bar.

Validation

• macOS Debug build and test: 696 tests passed.
• tvOS Debug simulator build and test: 61 tests passed, including Top Shelf coverage.
• Live Apple TV Home remote-navigation smoke test: 1 passed, 0 skipped.
• Staged diff whitespace check passed. Offline TruffleHog scan of all 201 changed files found no credential matches; remote credential verification was disabled.
• Corrected two stale episode-label expectations found during validation.
• Local source inspection completed for the update. External autoreview was blocked by automatic approval review and was not run for this diff.
• This pass did not rerun the full live playback/UI suite or validate signed device archives and distribution.