feat: Add SOLID principles and TDD reference documentation

- Created solid.md to document the SOLID principles for clean code practices.
- Created tdd.md to outline Test Driven Development principles and practices.
- Added kana-rust-backend-best-practice.md as a reference guide for building a Rust backend using Axum and SeaORM.
- Established push-flow-convention.md to enforce pre-commit and pre-push hooks with versioning rules.
- Introduced AGENTS.md to provide guidance on best practices and available commands for Kilo.
- Configured kilo.json to include new skills and agents for enhanced functionality.
- Added lefthook.yml for managing git hooks to ensure code quality and adherence to conventions.

apps/infrastructure/src/lib.rs

@@ -77,12 +77,14 @@ pub struct DirCache {
 }
 
 impl DirCache {
+    /// Create an empty directory cache.
     pub fn new() -> Self {
         DirCache {
             entries: Arc::new(tokio::sync::RwLock::new(Vec::new())),
         }
     }
 
+    /// Replace the cached directory entries.
     pub async fn set(&self, paths: Vec<PathBuf>) {
         let mut w = self.entries.write().await;
         *w = paths;
@@ -103,24 +105,28 @@ pub struct MentionIndex {
 }
 
 impl MentionIndex {
+    /// Create an empty mention index.
     pub fn new() -> Self {
         MentionIndex {
             entries: Arc::new(std::sync::RwLock::new(Vec::new())),
         }
     }
 
+    /// Replace the entire index with a new set of file paths.
     pub fn set(&self, paths: Vec<String>) {
         if let Ok(mut w) = self.entries.write() {
             *w = paths;
         }
     }
 
+    /// Append a single file path to the index.
     pub fn push(&self, path: String) {
         if let Ok(mut w) = self.entries.write() {
             w.push(path);
         }
     }
 
+    /// Return a copy of all indexed paths.
     pub fn snapshot(&self) -> Vec<String> {
         self.entries.read().map(|r| r.clone()).unwrap_or_default()
     }