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.

docs/deployment.md

@@ -38,12 +38,15 @@ package manager. Linux (primary), macOS, and Windows builds.
 
 ```bash
 git clone … && cd voice-cat
-cmake --preset server-release      # vcpkg fetches & pins all deps
+cmake --preset server-release      # vcpkg fetches & pins all deps; auto-triplet (Linux/macOS/Windows)
 cmake --build --preset server-release
-./build/voicecat-server
+./build/server-release/bin/voicecat-server
 ```
 
 One `cmake` invocation; vcpkg (manifest mode) resolves the dependency graph reproducibly.
+The `server-release` preset produces an optimized, **stripped** binary (`-s` linker flag) —
+smaller executables suitable for distribution. Works on Linux (primary), macOS, and Windows;
+the vcpkg triplet is auto-resolved by [`cmake/voicecat-toolchain.cmake`](../cmake/voicecat-toolchain.cmake).
 No system packages to chase.
 
 ## 2. Zero-config defaults