fix(tui): route bracketed paste to provider picker key entry instead of composer (#342)

Add handle_paste(text) -> ViewAction method to the ModalView trait with a
default no-op. ProviderPickerView overrides it in KeyEntry stage to
sanitize and append pasted text to api_key_input (rejecting whitespace
in the same way as the Char handler).

Wire into the Event::Paste handler in ui.rs: before falling through to
app.insert_paste_text(), check view_stack.handle_paste(). If the top
modal consumes the paste, skip the composer entirely. If a modal is
open but does NOT consume the paste, also skip the composer — any
modal that receives paste while focused should handle it, not leak
into the chat input.

crates/tui/src/tui/provider_picker.rs

@@ -246,6 +246,16 @@ impl ModalView for ProviderPickerView {
         self
     }
 
+    fn handle_paste(&mut self, text: &str) -> ViewAction {
+        if self.stage == Stage::KeyEntry {
+            let sanitized: String = text.chars().filter(|c| !c.is_whitespace()).collect();
+            if !sanitized.is_empty() {
+                self.api_key_input.push_str(&sanitized);
+            }
+        }
+        ViewAction::None
+    }
+
     fn handle_key(&mut self, key: KeyEvent) -> ViewAction {
         match self.stage {
             Stage::List => match key.code {

crates/tui/src/tui/ui.rs

@@ -1240,6 +1240,10 @@ async fn run_event_loop(
                     sync_api_key_validation_status(app, false);
                 } else if app.is_history_search_active() {
                     app.history_search_insert_str(text);
+                } else if app.view_stack.handle_paste(text) {
+                    // Modal consumed the paste (e.g. provider picker key entry)
+                } else if !app.view_stack.is_empty() {
+                    // A non-consumed modal is open — don't leak paste into composer
                 } else {
                     // Paste into main input
                     app.insert_paste_text(text);

crates/tui/src/tui/views/mod.rs

@@ -173,6 +173,9 @@ pub enum ViewAction {
 pub trait ModalView: std::any::Any {
     fn kind(&self) -> ModalKind;
     fn handle_key(&mut self, key: KeyEvent) -> ViewAction;
+    fn handle_paste(&mut self, _text: &str) -> ViewAction {
+        ViewAction::None
+    }
     fn handle_mouse(&mut self, _mouse: MouseEvent) -> ViewAction {
         ViewAction::None
     }
@@ -245,6 +248,13 @@ impl ViewStack {
         self.apply_action(action)
     }
 
+    pub fn handle_paste(&mut self, text: &str) -> bool {
+        self.views
+            .last_mut()
+            .map(|view| matches!(view.handle_paste(text), ViewAction::None))
+            .unwrap_or(false)
+    }
+
     pub fn handle_mouse(&mut self, mouse: MouseEvent) -> Vec<ViewEvent> {
         let action = self
             .views