New docs

docs/commands/dcr-build.md

@@ -1,2 +1,42 @@
 # dcr build
 
+Builds the project in `debug` or `release` profile.
+
+## Usage
+
+```sh
+dcr build
+dcr build --debug
+dcr build --release
+```
+
+## What `build` does
+
+1. Checks that `dcr.toml` exists and is valid.
+2. Reads build settings from `[build]`.
+3. Resolves path dependencies from `[dependencies]`.
+4. Creates required output directories.
+5. Recursively compiles sources from `src/`.
+6. Links final artifact (binary or static library).
+
+## Config values used
+
+- `package.name`
+- `build.compiler`
+- `build.language`
+- `build.standard`
+- `build.kind`
+- `build.target`
+- `build.cflags`
+- `build.ldflags`
+
+## Source selection
+
+- `language = "c"` -> `*.c`
+- `language = "c++" | "cpp" | "cxx"` -> `*.cpp`, `*.cxx`, `*.cc`
+
+## Notes
+
+- The profile is selected from the first argument only.
+- Unknown profile flags return an error.
+- Incremental rebuild is based on source/object mtime comparison.