init: archlens — architecture diagram generator

Hex arch + DDD, tree-sitter parsing, Mermaid/ASCII output.
Supports Rust + Python. 92 tests. CI, diff, --check for staleness detection.

crates/adapters/walkdir/src/walkdir_discovery.rs

@@ -0,0 +1,100 @@
+use std::path::Path;
+
+use ignore::WalkBuilder;
+
+use archlens_domain::{
+    AnalysisConfig, DomainError, FilePath, Language, SourceFile, ports::FileDiscovery,
+};
+
+const DEFAULT_EXCLUDES: &[&str] = &[
+    ".venv",
+    "venv",
+    "node_modules",
+    "__pycache__",
+    ".git",
+    "target",
+    "bin",
+    "obj",
+    "dist",
+    ".tox",
+    ".eggs",
+];
+
+pub struct WalkdirDiscovery;
+
+impl Default for WalkdirDiscovery {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl WalkdirDiscovery {
+    pub fn new() -> Self {
+        Self
+    }
+
+    fn detect_language(path: &Path) -> Option<Language> {
+        match path.extension()?.to_str()? {
+            "rs" => Some(Language::Rust),
+            "py" => Some(Language::Python),
+            "cs" => Some(Language::CSharp),
+            _ => None,
+        }
+    }
+
+    fn is_excluded(path: &Path, root: &Path, excludes: &[String]) -> bool {
+        let relative = path.strip_prefix(root).unwrap_or(path);
+        let relative_str = relative.to_string_lossy();
+
+        for component in relative.components() {
+            let name = component.as_os_str().to_string_lossy();
+            if DEFAULT_EXCLUDES.iter().any(|e| name == *e) {
+                return true;
+            }
+        }
+
+        excludes
+            .iter()
+            .any(|exclude| relative_str.contains(exclude.trim_end_matches('/')))
+    }
+}
+
+impl FileDiscovery for WalkdirDiscovery {
+    fn discover(
+        &self,
+        root: &Path,
+        config: &AnalysisConfig,
+    ) -> Result<Vec<SourceFile>, DomainError> {
+        let mut files = Vec::new();
+
+        let walker = WalkBuilder::new(root).hidden(true).git_ignore(true).build();
+
+        for entry in walker.filter_map(|e| e.ok()) {
+            let path = entry.path();
+
+            if !path.is_file() {
+                continue;
+            }
+
+            if Self::is_excluded(path, root, config.excludes()) {
+                continue;
+            }
+
+            if let Some(scope) = config.scope() {
+                let relative = path.strip_prefix(root).unwrap_or(path);
+                if !relative.starts_with(scope) {
+                    continue;
+                }
+            }
+
+            if let Some(language) = Self::detect_language(path) {
+                let absolute = path.canonicalize().unwrap_or_else(|_| path.to_path_buf());
+                let file_path = FilePath::new(&absolute.to_string_lossy())
+                    .map_err(|e| DomainError::IoError(e.to_string()))?;
+                files.push(SourceFile::new(file_path, language));
+            }
+        }
+
+        Ok(files)
+    }
+}