build(cmake): clean up presets, add release/apple presets, cross-platform triplets

Rationalize the preset set to match the project's actual state (past M5):
- Rename dev->skeleton (no-deps stub smoke), m1-dev->dev (default dev preset)
- Drop m2-dev (cache-identical to m1-dev)
- Add release preset (optimized + tests on, symbols kept)
- Strip server-release binaries (-s linker flag)
- Add apple-dev/apple-ios/apple-ios-sim scaffolding presets for XCFramework

Add cmake/voicecat-toolchain.cmake wrapper that auto-resolves the vcpkg
triplet from the host platform (x64-mingw-static/x64-linux/arm64-osx) so
the main presets work on Windows/Linux/macOS without per-OS variants.

Update all docs (building.md, CLAUDE.md, README.md, AGENTS.md, deployment.md,
tech-stack.md, client READMEs) and stale preset-name references in code
comments. No C++ behavior changes — the core was already portable.

README.md

@@ -5,10 +5,11 @@ channel-based voice, channel + private text, one server you run yourself. Plain
 (control) and **UDP** (media), no WebRTC. Encrypted by default. A shared **C++ core**
 (`libvoicecat`) drives native clients (Swift on macOS/iOS, C# on Windows) and the server.
 
-> **Status: pre-implementation.** The design is complete in [`docs/`](docs/). The code is an
-> M0 **skeleton** — it compiles and links, but every subsystem is a stub. See
-> [`AGENTS.md`](AGENTS.md) to start building, and [`docs/roadmap.md`](docs/roadmap.md) for the
-> milestones.
+> **Status:** Design complete in [`docs/`](docs/). M1–M5 are implemented — real TLS control
+> plane, encrypted UDP voice (Opus), multi-stream, TOFU identity pinning, channel tree,
+> permissions, moderation, disconnect/keepalive/reaper. Windows WinForms C# client shipped
+> (M4). macOS/iOS Swift client is next. See [`PROGRESS.md`](PROGRESS.md) and
+> [`docs/roadmap.md`](docs/roadmap.md).
 
 ## Read the design first
 
@@ -16,28 +17,34 @@ The [`docs/`](docs/) folder is the source of truth. Start at [`docs/README.md`](
 then `architecture` → `protocol` → `voice` → `security` → `tech-stack` → `deployment` →
 `roadmap`.
 
-## Build the skeleton (no dependencies needed yet)
+## Build
 
-The M0 skeleton builds with just a C++20 compiler + CMake + Ninja — **no vcpkg, no
-third-party libraries**, because every subsystem is currently a stub.
+The default development preset is **`dev`** — it builds everything (server + tools + tests)
+with real vcpkg deps. It works on Windows, Linux, and macOS (vcpkg triplet auto-resolved).
 
 ```bash
+# one-time vcpkg setup:
+git clone https://github.com/microsoft/vcpkg && ./vcpkg/bootstrap-vcpkg.sh  # .bat on Windows
+export VCPKG_ROOT=/path/to/vcpkg            # Linux/macOS; or $env:VCPKG_ROOT on PowerShell
+
+# configure + build + test:
 cmake --preset dev
 cmake --build --preset dev
-ctest --preset dev            # runs the smoke test (links the core, calls the C ABI)
+ctest --preset dev                          # 21 behavior tests
 ```
 
-Artifacts land in `build/dev/bin/` (`voicecat-server`, `vccli`).
+Artifacts land in `build/dev/bin/` (`voicecat-server`, `vccli`, `voicecat-admin`).
 
-When you start implementing a subsystem that needs real libraries, build with vcpkg deps:
+The `skeleton` preset (no vcpkg deps, stubs only) is a fast smoke check that needs no
+third-party libraries:
 
 ```bash
-# one-time: git clone https://github.com/microsoft/vcpkg && ./vcpkg/bootstrap-vcpkg.sh
-export VCPKG_ROOT=/path/to/vcpkg            # set VCPKG_ROOT (works on Linux/macOS/Windows)
-cmake --preset server-release               # auto-installs deps from vcpkg.json
-cmake --build --preset server-release
+cmake --preset skeleton && cmake --build --preset skeleton && ctest --preset skeleton
 ```
 
+See [`docs/building.md`](docs/building.md) for the full preset matrix (including `release`,
+`server-release`, `windows-client`, and Apple platform scaffolding).
+
 ## Layout
 
 ```