docs: rewrite documentation.

add: Nix and Snapcraft support.

docs/recipes/cross-to-windows.mdx

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+---
+sidebar_label: Cross-compile to Windows
+---
+
+# Cross-Compile to Windows from Linux
+
+Building a Windows binary on Linux using mingw-w64.
+
+## Install toolchain
+
+```bash
+# Ubuntu/Debian
+sudo apt install mingw-w64
+
+# Fedora
+sudo dnf install mingw64-gcc mingw64-binutils
+```
+
+## Configuration
+
+```toml
+[package]
+name = "my-app"
+version = "0.1.0"
+type = "none"
+
+[build]
+language = "c"
+standard = "c11"
+compiler = "clang"
+kind = "bin"
+target = "x86_64-pc-windows-gnu"    # explicit mingw, not msvc
+```
+
+## Build
+
+```bash
+dcr build --target x86_64-pc-windows-gnu --release
+```
+
+Artifact: `target/x86_64-pc-windows-gnu/release/my-app.exe`.
+
+## Custom toolchain
+
+```toml
+[toolchain]
+cc = "x86_64-w64-mingw32-gcc"
+cxx = "x86_64-w64-mingw32-g++"
+```

docs/recipes/library-project.mdx

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+---
+sidebar_label: Library project
+---
+
+# Library Project
+
+Creating a static library and using it in another project.
+
+## Step 1: Create the library
+
+```bash
+dcr new my-lib
+cd my-lib
+```
+
+`dcr.toml`:
+```toml
+[package]
+name = "my-lib"
+version = "0.1.0"
+type = "none"
+
+[build]
+language = "c"
+standard = "c11"
+kind = "staticlib"
+```
+
+`src/my_lib.h`:
+```c
+#ifndef MY_LIB_H
+#define MY_LIB_H
+int add(int a, int b);
+#endif
+```
+
+`src/my_lib.c`:
+```c
+#include "my_lib.h"
+int add(int a, int b) { return a + b; }
+```
+
+## Step 2: Build
+
+```bash
+dcr build --release
+```
+
+Artifacts:
+- `target/<triple>/release/libmy-lib.a` (Linux)
+- `target/release/my-lib.lib` (Windows)
+- `target/include/` — header files
+
+## Step 3: Use in another project
+
+```bash
+dcr new my-app
+cd my-app
+dcr add my-lib ../my-lib
+```
+
+Automatically:
+- Adds include path to `target/include/` of the library
+- Adds lib path to `target/<triple>/release/`
+- Links `libmy-lib.a` / `my-lib.lib`

docs/recipes/multi-package-workspace.mdx

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+---
+sidebar_label: Multi-package workspace
+---
+
+# Multi-Package Workspace
+
+A project with three packages: two libraries and a binary.
+
+## Structure
+
+```
+workspace/
+├── dcr.toml              # root workspace
+├── lib-core/
+│   ├── dcr.toml
+│   └── src/core.c
+├── lib-utils/
+│   ├── dcr.toml
+│   └── src/utils.c
+└── app/
+    ├── dcr.toml
+    └── src/main.c
+```
+
+## Root dcr.toml
+
+```toml
+[package]
+name = "my-workspace"
+version = "0.1.0"
+type = "none"
+
+[build]
+inherit = true
+language = "c"
+standard = "c11"
+
+[workspace.lib-core]
+path = "lib-core"
+
+[workspace.lib-utils]
+path = "lib-utils"
+deps = ["lib-core"]
+
+[workspace.app]
+path = "app"
+deps = ["lib-core", "lib-utils"]
+main = true
+```
+
+## Packages
+
+`lib-core/dcr.toml`:
+```toml
+[package]
+name = "lib-core"
+version = "0.1.0"
+type = "none"
+
+[build]
+kind = "staticlib"
+```
+
+`lib-utils/dcr.toml`:
+```toml
+[package]
+name = "lib-utils"
+version = "0.1.0"
+type = "none"
+
+[build]
+kind = "staticlib"
+```
+
+`app/dcr.toml`:
+```toml
+[package]
+name = "app"
+version = "0.1.0"
+type = "none"
+
+[build]
+kind = "bin"
+```
+
+## Build
+
+```bash
+cd workspace
+dcr build                     # builds everything in correct order
+dcr build --workspace app     # only app (lib-core and lib-utils built as deps)
+dcr run                       # builds and runs main package
+```
+
+Build order (topological sort):
+1. `lib-core`
+2. `lib-utils` (depends on lib-core)
+3. `app` (depends on lib-core, lib-utils)