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.

tests/CMakeLists.txt

@@ -6,7 +6,7 @@ target_link_libraries(test_smoke PRIVATE voicecat::voicecat)
 target_compile_features(test_smoke PRIVATE cxx_std_20)
 add_test(NAME smoke COMMAND test_smoke)
 
-# frame_codec has no third-party deps; runs under both dev and m1-dev.
+# frame_codec has no third-party deps; runs under both skeleton and dev.
 # Needs core/src on the include path to reach internal headers (protocol/, session/, etc.).
 add_executable(test_frame_codec test_frame_codec.cpp)
 target_link_libraries(test_frame_codec PRIVATE voicecat::voicecat)

tests/test_envelope.cpp

@@ -1,6 +1,6 @@
 /*
  * test_envelope — round-trip an Envelope through FrameCodec + encode/decode.
- * Runs only under m1-dev (requires protobuf).
+ * Runs only under dev (requires protobuf).
  */
 #include <cstdio>
 #include <cstring>

tests/test_frame_codec.cpp

@@ -1,7 +1,7 @@
 /*
  * test_frame_codec — unit test for FrameCodec::feed / ::emit.
  *
- * No third-party dependencies; runs under both the dev and m1-dev presets.
+ * No third-party dependencies; runs under both the skeleton and dev presets.
  * Tests: empty payload, single byte, 64 KiB, exact max-size, oversized (should reject),
  * split delivery (bytes fed one-at-a-time), and batched multi-frame delivery.
  */

tests/test_opus_codec.cpp

@@ -1,7 +1,7 @@
 /*
  * test_opus_codec — Opus encode/decode round-trip, PLC, energy check.
  *
- * Requires VOICECAT_HAS_OPUS (m1-dev and m2-dev presets).
+ * Requires VOICECAT_HAS_OPUS (dev and release presets).
  */
 #include <cmath>
 #include <cstdio>

tests/test_smoke.cpp

@@ -43,7 +43,7 @@ int main() {
     CHECK(vc_connect(c, nullptr, 1) == VC_ERR_INVALID_ARG);
     CHECK(vc_send_text(c, VC_TEXT_CHANNEL, 0, nullptr) == VC_ERR_INVALID_ARG);
 
-    // Under dev preset: NOT_IMPLEMENTED. Under m1-dev: VC_OK (async connect).
+    // Under skeleton preset: NOT_IMPLEMENTED. Under dev: VC_OK (async connect).
     vc_result rc_connect = vc_connect(c, "127.0.0.1", 8384);
     CHECK(rc_connect == VC_ERR_NOT_IMPLEMENTED || rc_connect == VC_OK);
 

tests/test_tcp_loopback.cpp

@@ -1,6 +1,6 @@
 /*
  * test_tcp_loopback — in-process TCP acceptor + client, sends 10 frames.
- * Runs only under m1-dev (requires Asio).
+ * Runs only under dev (requires Asio).
  */
 #include <atomic>
 #include <chrono>