refactor: modularize build core engine, update workspaces, cache, and test suite

docs/commands/project-commands.mdx

@@ -12,8 +12,12 @@ Only ASCII letters, digits, underscores `_` and hyphens `-` are allowed in the p
 
 ```bash
 dcr new my-app
+dcr new my-app --vcs none
 ```
 
+Flags:
+- `--vcs <git|none>` — Initialize version control system (defaults to `git` if available, or `none`).
+
 Generates:
 - `dcr.toml` with basic fields
 - `src/main.c` with a `main` template
@@ -23,8 +27,11 @@ Generates:
 Initializes a DCR project in the current (empty) directory.
 
 ```bash
-mkdir app && cd app
 dcr init
+dcr init --vcs none
 ```
 
+Flags:
+- `--vcs <git|none>` — Initialize version control system (defaults to `git` if available, or `none`).
+
 The project name is taken from the current directory name. The directory name must follow the same naming rules as `dcr new`.

docs/commands/system-commands.mdx

@@ -15,9 +15,9 @@ dcr setup
 If `~/.dcr/config.toml` is not found, DCR returns an error. Create it manually:
 
 ```toml
-[[registry]]
-name = "default"
+[registry.default]
 url = "https://index.dcr.pm"
+priority = 1
 ```
 
 ## `dcr --help`