feat(docs): create sukr documentation site

Self-documenting docs site built with sukr itself (dogfooding):
- docs/site.toml with sukr.io base URL
- docs-specific templates with sidebar navigation
- Dark theme CSS, responsive layout
- Documentation: getting-started, configuration, features

Also: improved error chaining for better template debugging

src/error.rs

@@ -42,12 +42,16 @@ pub enum Error {
     Config { path: PathBuf, message: String },
 
     /// Failed to load templates.
-    #[error("failed to load templates: {message}")]
-    TemplateLoad { message: String },
+    #[error("failed to load templates: {0}")]
+    TemplateLoad(#[source] tera::Error),
 
     /// Failed to render template.
-    #[error("failed to render template '{template}': {message}")]
-    TemplateRender { template: String, message: String },
+    #[error("failed to render template '{template}'")]
+    TemplateRender {
+        template: String,
+        #[source]
+        source: tera::Error,
+    },
 }
 
 /// Result type alias for compiler operations.

src/main.rs

@@ -35,6 +35,12 @@ fn main() {
         Ok(Some(config_path)) => {
             if let Err(e) = run(&config_path) {
                 eprintln!("error: {e}");
+                // Print full error chain
+                let mut source = std::error::Error::source(&e);
+                while let Some(cause) = source {
+                    eprintln!("  caused by: {cause}");
+                    source = std::error::Error::source(cause);
+                }
                 std::process::exit(1);
             }
         }

src/template_engine.rs

@@ -18,9 +18,7 @@ impl TemplateEngine {
     /// Load templates from a directory (glob pattern: `templates/**/*`).
     pub fn new(template_dir: &Path) -> Result<Self> {
         let pattern = template_dir.join("**/*").display().to_string();
-        let tera = Tera::new(&pattern).map_err(|e| Error::TemplateLoad {
-            message: e.to_string(),
-        })?;
+        let tera = Tera::new(&pattern).map_err(Error::TemplateLoad)?;
         Ok(Self { tera })
     }
 
@@ -30,7 +28,7 @@ impl TemplateEngine {
             .render(template_name, context)
             .map_err(|e| Error::TemplateRender {
                 template: template_name.to_string(),
-                message: e.to_string(),
+                source: e,
             })
     }