feat(app): add generation orchestration, messaging, and core App struct

Introduce `App` with provider manager, unbounded message channel, and active generation tracking.
Add `AppMessage` enum covering UI events, generation lifecycle (start, chunk, complete, error), model refresh, and provider status updates.
Implement `start_generation` to spawn asynchronous generation tasks, stream results, handle errors, and abort any previous generation.
Expose the new module via `pub mod app` in the crate root.

crates/owlen-tui/src/app/generation.rs

@@ -0,0 +1,77 @@
+use std::sync::Arc;
+
+use anyhow::{Result, anyhow};
+use futures_util::StreamExt;
+use owlen_core::provider::GenerateRequest;
+use uuid::Uuid;
+
+use super::{ActiveGeneration, App, AppMessage};
+
+impl App {
+    /// Kick off a new generation task on the supplied provider.
+    pub fn start_generation(
+        &mut self,
+        provider_id: impl Into<String>,
+        request: GenerateRequest,
+    ) -> Result<Uuid> {
+        let provider_id = provider_id.into();
+        let request_id = Uuid::new_v4();
+
+        // Cancel any existing task so we don't interleave output.
+        if let Some(active) = self.active_generation.take() {
+            active.abort();
+        }
+
+        self.message_tx
+            .send(AppMessage::GenerateStart {
+                request_id,
+                provider_id: provider_id.clone(),
+                request: request.clone(),
+            })
+            .map_err(|err| anyhow!("failed to queue generation start: {err:?}"))?;
+
+        let manager = Arc::clone(&self.provider_manager);
+        let message_tx = self.message_tx.clone();
+        let provider_for_task = provider_id.clone();
+
+        let join_handle = tokio::spawn(async move {
+            let mut stream = match manager.generate(&provider_for_task, request).await {
+                Ok(stream) => stream,
+                Err(err) => {
+                    let _ = message_tx.send(AppMessage::GenerateError {
+                        request_id: Some(request_id),
+                        message: err.to_string(),
+                    });
+                    return;
+                }
+            };
+
+            while let Some(chunk_result) = stream.next().await {
+                match chunk_result {
+                    Ok(chunk) => {
+                        if message_tx
+                            .send(AppMessage::GenerateChunk { request_id, chunk })
+                            .is_err()
+                        {
+                            break;
+                        }
+                    }
+                    Err(err) => {
+                        let _ = message_tx.send(AppMessage::GenerateError {
+                            request_id: Some(request_id),
+                            message: err.to_string(),
+                        });
+                        return;
+                    }
+                }
+            }
+
+            let _ = message_tx.send(AppMessage::GenerateComplete { request_id });
+        });
+
+        let generation = ActiveGeneration::new(request_id, provider_id, join_handle);
+        self.active_generation = Some(generation);
+
+        Ok(request_id)
+    }
+}

crates/owlen-tui/src/app/messages.rs

@@ -0,0 +1,41 @@
+use crossterm::event::KeyEvent;
+use owlen_core::provider::{GenerateChunk, GenerateRequest, ProviderStatus};
+use uuid::Uuid;
+
+/// Messages exchanged between the UI event loop and background workers.
+#[derive(Debug)]
+pub enum AppMessage {
+    /// User input event bubbled up from the terminal layer.
+    KeyPress(KeyEvent),
+    /// Terminal resize notification.
+    Resize { width: u16, height: u16 },
+    /// Periodic tick used to drive animations.
+    Tick,
+    /// Initiate a new text generation request.
+    GenerateStart {
+        request_id: Uuid,
+        provider_id: String,
+        request: GenerateRequest,
+    },
+    /// Streamed response chunk from the active generation task.
+    GenerateChunk {
+        request_id: Uuid,
+        chunk: GenerateChunk,
+    },
+    /// Generation finished successfully.
+    GenerateComplete { request_id: Uuid },
+    /// Generation failed or was aborted.
+    GenerateError {
+        request_id: Option<Uuid>,
+        message: String,
+    },
+    /// Trigger a background refresh of available models.
+    ModelsRefresh,
+    /// New model list data is ready.
+    ModelsUpdated,
+    /// Provider health status update.
+    ProviderStatus {
+        provider_id: String,
+        status: ProviderStatus,
+    },
+}

crates/owlen-tui/src/app/mod.rs

@@ -0,0 +1,80 @@
+mod generation;
+
+pub mod messages;
+
+use std::sync::Arc;
+
+use owlen_core::provider::ProviderManager;
+use tokio::{
+    sync::mpsc,
+    task::{AbortHandle, JoinHandle},
+};
+use uuid::Uuid;
+
+pub use messages::AppMessage;
+
+/// High-level application state driving the non-blocking TUI.
+pub struct App {
+    provider_manager: Arc<ProviderManager>,
+    message_tx: mpsc::UnboundedSender<AppMessage>,
+    #[allow(dead_code)]
+    message_rx: mpsc::UnboundedReceiver<AppMessage>,
+    active_generation: Option<ActiveGeneration>,
+}
+
+impl App {
+    /// Construct a new application instance with an associated message channel.
+    pub fn new(provider_manager: Arc<ProviderManager>) -> Self {
+        let (message_tx, message_rx) = mpsc::unbounded_channel();
+
+        Self {
+            provider_manager,
+            message_tx,
+            message_rx,
+            active_generation: None,
+        }
+    }
+
+    /// Cloneable sender handle for pushing messages into the application loop.
+    pub fn message_sender(&self) -> mpsc::UnboundedSender<AppMessage> {
+        self.message_tx.clone()
+    }
+
+    /// Whether a generation task is currently in flight.
+    pub fn has_active_generation(&self) -> bool {
+        self.active_generation.is_some()
+    }
+
+    /// Abort any in-flight generation task.
+    pub fn abort_active_generation(&mut self) {
+        if let Some(active) = self.active_generation.take() {
+            active.abort();
+        }
+    }
+}
+
+struct ActiveGeneration {
+    #[allow(dead_code)]
+    request_id: Uuid,
+    #[allow(dead_code)]
+    provider_id: String,
+    abort_handle: AbortHandle,
+    #[allow(dead_code)]
+    join_handle: JoinHandle<()>,
+}
+
+impl ActiveGeneration {
+    fn new(request_id: Uuid, provider_id: String, join_handle: JoinHandle<()>) -> Self {
+        let abort_handle = join_handle.abort_handle();
+        Self {
+            request_id,
+            provider_id,
+            abort_handle,
+            join_handle,
+        }
+    }
+
+    fn abort(self) {
+        self.abort_handle.abort();
+    }
+}

crates/owlen-tui/src/lib.rs

@@ -14,6 +14,7 @@
 //! - `events`: Event handling for user input and other asynchronous actions.
 //! - `ui`: The rendering logic for all TUI components.
 
+pub mod app;
 pub mod chat_app;
 pub mod code_app;
 pub mod commands;