Keep the composer editable during TUI startup (#38642)

## Why

Configuration and app-server initialization can take time before the main TUI is ready, leaving users unable to begin drafting a prompt.

## What changed

- Show a provisional composer while startup work runs and carry its text, cursor position, paste state, and attachments into the initialized chat.
- Limit the provisional composer to safe editing and cancellation, and quarantine input around session pickers, approvals, and other actionable startup screens.
- Preserve configuration validation before terminal checks and recover terminal state cleanly from startup failures and caught panics.

## Testing

- Cover startup editing, multiline and large pastes, keymaps, cancellation, session-picker handoff, approval boundaries, and draft restoration.
- Verify non-interactive launches report configuration errors before terminal errors.

GitOrigin-RevId: fe04a85cfbbcff21ff87fa81fd17474827858575

codex-rs/tui/src/bottom_pane/mod.rs

@@ -156,6 +156,7 @@ mod scroll_state;
 mod selection_popup_common;
 mod selection_row_layout;
 mod selection_tabs;
+mod startup;
 mod textarea;
 mod unified_exec_footer;
 pub(crate) use feedback_view::FeedbackNoteView;
@@ -194,6 +195,7 @@ pub(crate) enum CancellationEvent {
 use crate::bottom_pane::prompt_args::parse_slash_name;
 pub(crate) use chat_composer::ChatComposer;
 pub(crate) use chat_composer::ChatComposerConfig;
+pub(crate) use chat_composer::ComposerDraftSnapshot;
 pub(crate) use chat_composer::InputResult;
 pub(crate) use chat_composer::QueuedInputAction;
 pub(crate) use chat_composer_history::HistoryEntry;
@@ -267,6 +269,14 @@ pub(crate) struct BottomPaneParams {
 
 impl BottomPane {
     pub fn new(params: BottomPaneParams) -> Self {
+        Self::new_with_composer_config(params, ChatComposerConfig::default())
+    }
+
+    /// Construct a bottom pane with explicitly restricted composer behavior.
+    pub(crate) fn new_with_composer_config(
+        params: BottomPaneParams,
+        composer_config: ChatComposerConfig,
+    ) -> Self {
         let BottomPaneParams {
             app_event_tx,
             frame_requester,
@@ -277,12 +287,13 @@ impl BottomPane {
             animations_enabled,
             skills,
         } = params;
-        let mut composer = ChatComposer::new(
+        let mut composer = ChatComposer::new_with_config(
             has_input_focus,
             app_event_tx.clone(),
             enhanced_keys_supported,
             placeholder_text,
             disable_paste_burst,
+            composer_config,
         );
         composer.set_frame_requester(frame_requester.clone());
         let keymap = RuntimeKeymap::defaults();
@@ -577,7 +588,7 @@ impl BottomPane {
 
     fn record_composer_activity_at(&mut self, now: Instant) {
         self.last_composer_activity_at = Some(now);
-        if !self.delayed_approval_requests.is_empty()
+        if self.has_pending_approval()
             && let Some(delay) = self.approval_prompt_delay_remaining(now)
         {
             self.request_redraw_in(delay);
@@ -585,7 +596,7 @@ impl BottomPane {
     }
 
     fn maybe_show_delayed_approval_requests_at(&mut self, now: Instant) {
-        if self.delayed_approval_requests.is_empty() || !self.view_stack.is_empty() {
+        if !self.has_pending_approval() || !self.view_stack.is_empty() {
             return;
         }
         if let Some(delay) = self.approval_prompt_delay_remaining(now) {
@@ -884,10 +895,6 @@ impl BottomPane {
         self.composer.cursor()
     }
 
-    pub(crate) fn composer_draft_snapshot(&self) -> chat_composer::ComposerDraftSnapshot {
-        self.composer.draft_snapshot()
-    }
-
     #[cfg(test)]
     pub(crate) fn composer_text_elements(&self) -> Vec<TextElement> {
         self.composer.text_elements()