R1-03: Core strong types

.github/workflows/pr.yml

@@ -62,8 +62,11 @@ jobs:
           - name: linux-release
             os: ubuntu-24.04
             preset: release
+          # macos-15 = Xcode 16 (AppleClang 16 / libc++ 18): complete std::format
+          # for custom formatters. macos-14 (Xcode 15, libc++ 16) has incomplete
+          # std::format support and is below the project floor (BUILD_SYSTEM.md).
           - name: macos-debug
-            os: macos-14
+            os: macos-15
             preset: debug
     steps:
       - uses: actions/checkout@v4

README.md

@@ -12,7 +12,7 @@ Release 1 milestone; until then this file is developer-facing.
 
 ## Development
 
-Requirements: CMake ≥ 3.27, Ninja, a C++20 compiler (AppleClang 15+ / Clang 16+ / GCC 13+).
+Requirements: CMake ≥ 3.27, Ninja, a C++20 compiler (AppleClang 16+ / Clang 16+ / GCC 13+).
 Build tooling and rationale are documented in
 [`docs/build/BUILD_SYSTEM.md`](docs/build/BUILD_SYSTEM.md).
 

docs/build/BUILD_SYSTEM.md

@@ -1,8 +1,15 @@
 # Build System
 
 CMake ≥ 3.27, C++20 (S1), FetchContent-pinned dependencies (S2). One-command builds on macOS
-(AppleClang ≥ 15) and Linux (Clang ≥ 16, GCC ≥ 13 as the second compiler for warning
-diversity).
+(**AppleClang ≥ 16** — Xcode 16+) and Linux (Clang ≥ 16, GCC ≥ 13 as the second compiler for
+warning diversity).
+
+> **macOS floor is AppleClang 16, not 15.** `std::format` support for *custom* formatters is
+> incomplete in the libc++ shipped with Xcode 15 (libc++ 16): the consteval format-string
+> check does not recognize user-defined `std::formatter` specializations. libc++ 17+
+> (Xcode 16) is complete. CI runs `macos-15` for this reason (task R1-03 finding). If macOS 15
+> support ever becomes necessary, the alternative is to route formatting through `fmt` (a
+> planned dependency) instead of `std::format`.
 
 ## Presets (`CMakePresets.json` — the only supported way to configure)
 

docs/build/CI_PLAN.md

@@ -14,7 +14,7 @@ GitHub Actions, free tier only. Fast feedback per PR; heavy work nightly; nothin
 | `linux-debug` | ubuntu | debug preset: unit + property(CI budget) + differential + replay tests |
 | `linux-asan` | ubuntu | asan-ubsan preset: same suite |
 | `linux-release` | ubuntu | release preset: full test suite + 60s/target fuzz smoke |
-| `macos` | macos-14 (arm64) | debug + asan: full C++ suite (platform diversity catches real bugs) |
+| `macos` | macos-15 (arm64, Xcode 16) | debug: full C++ suite (platform diversity catches real bugs; Xcode 16 for complete std::format, see BUILD_SYSTEM.md) |
 | `python` | ubuntu + macos | build wheel, pytest (binding + micro-E2E: run→store→analyze→reproduce on 2-seed micro configs), nbconvert-execute notebooks on micro outputs |
 | `bench-smoke` | ubuntu | 3-benchmark subset vs stored runner baseline, **labeled unstable**, regression >25% fails (gross breakage only — real gates run on the dev Mac per METHODOLOGY) |
 

src/core/CMakeLists.txt

@@ -1 +1 @@
-microsim_add_library(core src/module_info.cpp)
+microsim_add_library(core src/module_info.cpp src/types.cpp)