New docs

docs/dependencies-and-build/compilers-and-linking.md

@@ -1,2 +1,30 @@
 # Compilers & linking
 
+## Compiler backend selection
+
+DCR picks a backend from `build.compiler`:
+
+- contains `clang-cl` -> MSVC backend
+- contains `gcc` or `g++` -> GCC backend
+- contains `clang` or `clang++` -> Clang backend
+- equals `cl` or contains `msvc` -> MSVC backend
+- otherwise -> Clang backend fallback
+
+## Compilation model
+
+- Source files are found recursively in `src/` based on `build.language`.
+- Each source is compiled to `target/<profile>/obj/<relative-path>.o` (`.obj` on MSVC).
+- Recompile happens when source mtime is newer than object mtime.
+
+## Linking
+
+For `kind = "bin"`:
+
+- Object files are linked into executable artifact.
+- Dependency lib dirs and library names are passed to linker.
+- `build.ldflags` are appended to link command.
+
+For `kind = "staticlib"`:
+
+- Linux/macOS (GCC/Clang): `ar rcs` creates `.a` archive.
+- Windows (MSVC): `lib` creates `.lib` archive.