Add comprehensive documentation and examples for Owlen architecture and usage

- Include detailed architecture overview in `docs/architecture.md`.
- Add `docs/configuration.md`, detailing configuration file structure and settings.
- Provide a step-by-step provider implementation guide in `docs/provider-implementation.md`.
- Add frequently asked questions (FAQ) document in `docs/faq.md`.
- Create `docs/migration-guide.md` for future breaking changes and version upgrades.
- Introduce new examples in `examples/` showcasing basic chat, custom providers, and theming.
- Add a changelog (`CHANGELOG.md`) for tracking significant changes.
- Provide contribution guidelines (`CONTRIBUTING.md`) and a Code of Conduct (`CODE_OF_CONDUCT.md`).

docs/provider-implementation.md

@@ -0,0 +1,75 @@
+# Provider Implementation Guide
+
+This guide explains how to implement a new provider for Owlen. Providers are the components that connect to different LLM APIs.
+
+## The `Provider` Trait
+
+The core of the provider system is the `Provider` trait, located in `owlen-core`. Any new provider must implement this trait.
+
+Here is a simplified version of the trait:
+
+```rust
+use async_trait::async_trait;
+use owlen_core::model::Model;
+use owlen_core::session::Session;
+
+#[async_trait]
+pub trait Provider {
+    /// Returns the name of the provider.
+    fn name(&self) -> &str;
+
+    /// Sends the session to the provider and returns the response.
+    async fn chat(&self, session: &Session, model: &Model) -> Result<String, anyhow::Error>;
+}
+```
+
+## Creating a New Crate
+
+1.  **Create a new crate** in the `crates/` directory. For example, `owlen-myprovider`.
+2.  **Add dependencies** to your new crate's `Cargo.toml`. You will need `owlen-core`, `async-trait`, `tokio`, and any crates required for interacting with the new API (e.g., `reqwest`).
+3.  **Add the new crate to the workspace** in the root `Cargo.toml`.
+
+## Implementing the Trait
+
+In your new crate's `lib.rs`, you will define a struct for your provider and implement the `Provider` trait for it.
+
+```rust
+use async_trait::async_trait;
+use owlen_core::model::Model;
+use owlen_core::provider::Provider;
+use owlen_core::session::Session;
+
+pub struct MyProvider;
+
+#[async_trait]
+impl Provider for MyProvider {
+    fn name(&self) -> &str {
+        "my-provider"
+    }
+
+    async fn chat(&self, session: &Session, model: &Model) -> Result<String, anyhow::Error> {
+        // 1. Get the conversation history from the session.
+        let history = session.get_messages();
+
+        // 2. Format the request for your provider's API.
+        //    This might involve creating a JSON body with the messages.
+
+        // 3. Send the request to the API using a client like reqwest.
+
+        // 4. Parse the response from the API.
+
+        // 5. Return the content of the response as a String.
+
+        Ok("Hello from my provider!".to_string())
+    }
+}
+```
+
+## Integrating with Owlen
+
+Once your provider is implemented, you will need to integrate it into the main Owlen application.
+
+1.  **Add your provider crate** as a dependency to `owlen-cli`.
+2.  **In `owlen-cli`, modify the provider registration** to include your new provider. This will likely involve adding it to a list of available providers that the user can select from in the configuration.
+
+This guide provides a basic outline. For more detailed examples, you can look at the existing provider implementations, such as `owlen-ollama`.