docs: Add rustdoc for filter_plugin, binary_detection, and lib.rs

Co-authored-by: aider (openai/andrew/openrouter/sonoma-sky-alpha) <aider@aider.chat>

src/lib.rs

@@ -2,6 +2,32 @@
 #![deny(unsafe_code)]
 #![allow(unused_imports)]
 
+//! Keep library for managing temporary files with compression and metadata.
+//!
+//! This library provides core functionality for the Keep application, including
+//! database operations, compression engines, item services, and plugin systems
+//! for metadata and filtering. It supports CLI modes, server APIs, and plugin
+//! registration via ctors.
+//!
+//! # Usage
+//!
+//! Add to Cargo.toml and use re-exported types:
+//! ```toml
+//! [dependencies]
+//! keep = "0.1"
+//! ```
+//!
+//! ```rust
+//! use keep::Args;
+//! let args = Args::parse();
+//! ```
+//!
+//! # Features
+//!
+//! - `server`: Enables Axum-based HTTP server.
+//! - `gzip`, `lz4`: Built-in compression support.
+//! - `magic`: File type detection via libmagic.
+
 // Re-export modules for testing
 pub mod common;
 pub mod compression_engine;
@@ -39,7 +65,16 @@ use meta_plugin::{
 #[allow(unused_imports)]
 use meta_plugin::magic_file;
 
-// Initialize plugins at library load time
+/// Initializes plugins at library load time.
+///
+/// Ensures all filter and meta plugins are registered via their ctors.
+/// Call this early in application startup if needed (though ctors handle most cases).
+///
+/// # Examples
+///
+/// ```
+/// keep::init_plugins();
+/// ```
 pub fn init_plugins() {
     // This will be expanded in Step 3 implementation
     // For now, the ctors handle registration