feat(apple): VoiceCatCore Swift package + XCFramework build for macOS/iOS clients

Lays the groundwork for the macOS (AppKit) and iOS (SwiftUI) clients with a shared
Swift core wrapping the C ABI, mirroring the proven Windows VoiceCat.Interop layer.

Architecture decision: macOS UI = AppKit (not SwiftUI) for the most mature VoiceOver
accessibility story — same rationale as the Windows client's WinForms-over-WinUI-3
decision. iOS stays SwiftUI. Recorded in docs/roadmap.md §2.

Build infrastructure (Phase 0):
- clients/apple/scripts/build-xcframework.sh: runs cmake --preset apple-dev, merges
  libvoicecat.a + 107 vcpkg static deps into a single ~30 MB fat static library
  (libvoicecat-fat.a) via libtool -static (SPM binary targets link one .a per slice),
  stages voicecat.h + a generated module.modulemap (module VoiceCatC) into the headers,
  runs xcodebuild -create-xcframework -> clients/apple/VoiceCatCore.xcframework.

VoiceCatCore Swift Package (Phase 1):
- Package.swift: binary target (VoiceCatCoreXCF) + library (VoiceCatCore) + test target.
- Sources/VoiceCatCore/: 7 files mirroring the C# VoiceCat.Interop patterns adapted to
  Swift native C interop — Enums (9 Swift mirrors of C enums, UInt32-backed), Config,
  Event (copies ev.text to String inside the callback — the #1 lifetime rule), Models
  (10 Swift value types), Marshaling (C arrays -> Swift + immediate vc_free_*),
  Callbacks (@convention(c) + Unmanaged.passUnretained, the Swift analog of C#'s
  [UnmanagedCallersOnly] + GCHandle), VoiceCatClient (owns vc_client* as OpaquePointer,
  all 38 C ABI functions, deinit -> vc_client_destroy then frees config CStrings, event
  delivery on main queue via coalesced DispatchQueue.main drain).

Tests — 6/6 green (swift test against a real voicecat-server):
- testConnectTofuAuthListChannelsRoundTrips, testAdminChannelCrudAccountCrudRoundTrips,
  testScreenAudioStreamStartsAndStops, testPerStreamRecvControlsRoundTrip, plus two
  static smoke tests. Catches Swift-specific interop bugs (@convention(c) callback
  lifetime, Unmanaged pointer resolution, CString memory management, enum raw-value
  bridging, struct layout) that C++ ctest cannot. C++ suite still 21/21 green.

Docs updated (house rule): tech-stack.md §2, architecture.md §4, roadmap.md M4 + §2,
clients/apple/README.md (full rewrite), PROGRESS.md, .gitignore.

docs/tech-stack.md

@@ -27,10 +27,12 @@ explicit resampling (speexdsp/libsamplerate) is only needed when a device can't
 
 | Concern | Choice | Notes |
 |---------|--------|-------|
-| Language | **Swift 5.9+** | Direct **Swift↔C++ interop** available, but we bind through the C ABI for parity with Windows. |
-| UI | **SwiftUI** | Single UI codebase for macOS + iOS where practical; AppKit/UIKit shims as needed. |
-| Audio session (iOS) | **AVAudioSession** | App owns category `.playAndRecord` + `.voiceChat` mode, mic permission, interruption/route-change handling; calls `vc_audio_suspend/resume` on the core. macOS uses CoreAudio via the core directly. |
-| Packaging | Swift Package + Xcode project | Core shipped as an XCFramework (device + simulator + macOS slices). |
+| Language | **Swift 5.9+** | Direct **Swift↔C interop** — the C ABI (`voicecat.h`) is imported as a Clang module (`import VoiceCatC`) via a module map in the XCFramework headers; no manual struct/function redeclaration (unlike the C# P/Invoke layer). A Swift wrapper (`VoiceCatCore` package) provides Swift-idiomatic types on top. |
+| UI — macOS | **AppKit** | Chosen over SwiftUI for the most mature, granular **VoiceOver** accessibility story (per-control `accessibilityLabel`/`accessibilityHelp`/`accessibilityRole`, `NSAccessibility.post(.announcement)` for live announcements) — the same rationale that drove the Windows client to WinForms over WinUI 3 for screen-reader (NVDA/JAWS/Narrator) UIA support (resolved decision in `docs/roadmap.md`). macOS 14 (Sonoma) deployment target. |
+| UI — iOS | **SwiftUI** | iOS has a narrower control surface (no channel-tree moderation, etc.) and SwiftUI's VoiceOver support is sufficient; revisit if gaps emerge. |
+| Shared core | **VoiceCatCore** Swift Package | One Swift library wrapping the C ABI, consumed by both the macOS AppKit app and the iOS SwiftUI app. Mirrors the C# `VoiceCat.Interop` layer. Events delivered on `@MainActor` via a coalesced `DispatchQueue.main` drain (the Swift analog of C#'s `Channel<VoiceCatEvent>` + 30ms WinForms Timer pump). |
+| Audio session (iOS) | **AVAudioSession** | App owns category `.playAndRecord` + `.voiceChat` mode, mic permission, interruption/route-change handling; calls `vc_audio_suspend/resume` on the core. macOS uses CoreAudio via the core directly. (`vc_audio_suspend`/`vc_audio_resume` ABI hooks are deferred until the iOS client milestone — keep ABI stable.) |
+| Packaging | Swift Package + Xcode project | Core shipped as an **XCFramework** binary target — a fat static library (`libvoicecat-fat.a`) bundling `libvoicecat.a` + all vcpkg static deps (protobuf/mbedtls/sodium/opus/sqlite3/spdlog/asio), so the Swift Package links a single self-contained `.a` per slice. macOS slice validated; iOS device + sim slices are scaffolding. |
 | Future | CallKit / PushKit | For background VoIP + incoming-call UX on iOS. Post-v1. |
 
 ### Windows — C# (shipped in M4, 2026-06-17)